# Condensed Matter

## New submissions

[ total of 95 entries: 1-95 ]
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### New submissions for Thu, 21 Sep 17

[1]
Title: Low-frequency phase diagram of irradiated graphene and periodically driven spin-1/2 $XY$ chain
Comments: v1; 26 pages, 19 Figs
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)

We study the Floquet phase diagram of two-dimensional Dirac materials such as graphene and the one-dimensional (1D) spin-1/2 $XY$ model in a transverse field in the presence of periodic time-varying terms in their Hamiltonians in the low drive frequency ($\omega$) regime where standard $1/\omega$ perturbative expansions fail. For graphene, such periodic time dependent terms are generated via the application of external radiation of amplitude $A_0$ and time period $T = 2\pi/\omega$, while for the 1D $XY$ model, they result from a two-rate drive protocol with time-dependent magnetic field and nearest-neighbor couplings between the spins. Using the adiabatic-impulse method, we provide several semi-analytic criteria for the occurrence of changes in the topology of the phase bands of such systems. For irradiated graphene, we point out the role of the symmetries of $H(t)$ and $U$ behind such topology changes. Our analysis reveals that at low frequencies, phase band topology changes may also happen at $t= T/3, 2T/3$ (apart from $t=T$). We chart out the phase diagrams at $t=T/3, 2T/3,\, {\rm and }\, T$ as a function of $A_0$ and $T$ using exact numerics, and compare them with the prediction of the adiabatic-impulse method. We show that several characteristics of these phase diagrams can be analytically understood from results obtained using the adiabatic-impulse method and point out the crucial contribution of the high-symmetry points in the graphene Brillouin zone to these diagrams. Finally we study the 1D $XY$ model with a two-rate driving protocol using the adiabatic-impulse method and exact numerics revealing a phase band crossing at $t=T/2$ and $k=\pi/2$. We also study the anomalous end modes generated by such a drive. We suggest experiments to test our theory.

[2]
Title: Localization and Oscillations in Majorana Fermions from $d$-Wave Superconductors
Subjects: Superconductivity (cond-mat.supr-con)

We study the localization and oscillation properties of the Majorana fermions that arise in a two-dimensional electron gas (2DEG) with spin-orbit coupling (SOC) and a Zeeman field coupled with a $d$-wave superconductor. Despite the angular dependence of the $d$-wave pairing, localization and oscillation properties are found to be similar to the ones seen in conventional $s$-wave superconductors. In addition, we study a microscopic lattice version of the previous system that can be characterized by a topological invariant. We derive its real space representation that involves nearest and next-to-nearest-neighbors pairing. Finally, we show that the emerging chiral Majorana fermions are indeed robust against static disorder. This analysis has potential applications to quantum simulations and experiments in high-$T_c$ superconductors.

[3]
Title: Particle-hole character of the Higgs and Goldstone modes in strongly-interacting lattice bosons
Subjects: Quantum Gases (cond-mat.quant-gas); Strongly Correlated Electrons (cond-mat.str-el); Superconductivity (cond-mat.supr-con)

We study the low-energy excitations of the Bose-Hubbard model in the strongly-interacting superfluid phase using a Gutzwiller approach and extract the single-particle and single-hole excitation amplitudes for each mode. We report emergent mode-dependent particle-hole symmetry on specific arc-shaped lines in the phase diagram connecting the well-known Lorentz-invariant limits of the Bose-Hubbard model. By tracking the in-phase particle-hole symmetric oscillations of the order parameter, we provide an answer to the long-standing question about the fate of the pure amplitude Higgs mode away from the integer-density critical point. Furthermore, we point out that out-of-phase oscillations are responsible for a full suppression of the condensate density oscillations of the gapless Goldstone mode. Possible detection protocols are also discussed.

[4]
Title: Interplay of Coulomb interactions and disorder in three dimensional quadratic band crossings without time-reversal or particle-hole symmetry
Subjects: Strongly Correlated Electrons (cond-mat.str-el); Disordered Systems and Neural Networks (cond-mat.dis-nn)

Coulomb interactions famously drive three dimensional quadratic band crossing semimetals into a non-Fermi liquid phase of matter. In a previous work, Phys. Rev. B 95, 205106 (2017) the effect of disorder on this non-Fermi liquid phase was investigated, assuming that the bandstructure was particle-hole symmetric and isotropic, and assuming that the disorder preserved exact time-reversal symmetry and statistical isotropy. It was shown that the non-Fermi liquid fixed point is unstable to disorder, and that a runaway flow to strong disorder occurs. In this work, we extend that analysis by relaxing the twin assumptions of time-reversal and particle-hole symmetry (but continuing to assume isotropy of the low energy bandstructure). We first incorporate time-reversal symmetry breaking disorder, and demonstrate that there do not appear any new fixed points. Moreover, while the system continues to flow to strong disorder, time-reversal-symmetry-breaking disorder grows asymptotically more slowly than time-reversal-symmetry-preserving disorder, which we therefore expect should dominate the strong-coupling phase. We then introduce a perturbation that breaks the particle-hole symmetry of the bandstructure. We show that whereas this perturbation is irrelevant in the clean system, it is relevant in the presence of disorder, such that the `effective masses' of the conduction and valence bands should become sharply distinct in the low-energy limit. We calculate the RG flow equations for the disordered interacting system in the presence of particle-hole symmetry breaking in the bandstructure, and demonstrate that the problem exhibits a runaway flow to strong disorder. Along the runaway flow, time-reversal-symmetry-preserving disorder grows asymptotically more rapidly than both time-reversal-symmetry-breaking disorder and the Coulomb interaction.

[5]
Title: Imaging interferometry of excitons in two-dimensional structures: Can it detect exciton coherence
Subjects: Other Condensed Matter (cond-mat.other)

Using the theory of imaging with partially coherent light, we derive general expressions for different kinds of interferometric setups like double slit, shift and mirror interference. We show that in all cases the interference patterns depend not only on the point spread function of the imaging setup but also strongly on the spatial emission pattern of the sample. Taking typical experimentally observed spatial emission patterns into account, we can reproduce at least qualitatively all the observed interference structures, which have been interpreted as signatures for spontaneous long range coherence of excitons, already for incoherent emitters. This requires a critical reexamination of the previous work.

[6]
Title: Microwave impedance of a dc-biased Josephson Fluxonic Diode in the presence of magnetic field and rf drive
Subjects: Superconductivity (cond-mat.supr-con)

The dependence of microwave impedance of a dc-biased Josephson Fluxonic Diode (JFD) under application of both dc magnetic field and rf excitation is calculated with a variety of conditions. For finite length of a JFD excited by a very low microwave excitation below its plasma frequency, applied dc magnetic field increases the rate of Vortex and Anti-Vortex (VAV) pair generation which fine-tunes the microwave resistance up to several factors more than its zero field microwave resistance (R0). Under this circumstance, adding a dc bias for moving VAVs causes oscillation-like features in microwave impedance of JFD either in forward or reverse bias. As a result, the microwave resistance increases up to 30R0 in the forward bias despite the fact that damping parameter (\b{eta}) can limit this increase. On the other hand, sharp phase slips are seen in reverse bias mode on the reactance of overdamped JFD while increasing the frequency or amplitude of microwave excitation leads to unprecedented effects of resistance which is described.

[7]
Title: Frequency pulling and mixing of relaxation oscillations in superconducting nanowires
Subjects: Superconductivity (cond-mat.supr-con)

Many superconducting technologies such as rapid single flux quantum computing (RSFQ) and superconducting quantum interference devices (SQUIDs) rely on the modulation of nonlinear dynamics in Josephson junctions for functionality. More recently, however, superconducting devices have been developed based on the switching and thermal heating of nanowires for use in fields such as single photon detection and digital logic. In this paper, we use resistive shunting to control the nonlinear heating of a superconducting nanowire and compare the resulting dynamics to those observed in Josephson junctions. We show that interaction of the hotspot growth with the external shunt produces high frequency relaxation oscillations with similar behavior as observed in Josephson junctions due to their rapid time constants and ability to be modulated by a weak periodic signal. In particular, we use a microwave drive to pull and mix the oscillation frequency, resulting in phase locked features that resemble the AC Josephson effect. New nanowire devices based on these conclusions have promising applications in fields such as parametric amplification and frequency multiplexing.

[8]
Title: The bilinear-biquadratic model on the complete graph
Subjects: Statistical Mechanics (cond-mat.stat-mech); Mathematical Physics (math-ph); Quantum Physics (quant-ph)

We study the spin-1 bilinear-biquadratic model on the complete graph of N sites, i.e., when each spin is interacting with every other spin with the same strength. Because of its complete permutation invariance, this Hamiltonian can be rewritten as the linear combination of the quadratic Casimir operators of su(3) and su(2). Using group representation theory, we explicitly diagonalize the Hamiltonian and map out the ground-state phase diagram of the model. Furthermore, the complete energy spectrum, with degeneracies, is obtained analytically for any number of sites.

[9]
Title: Demagnetizing fields in all-optical switching
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)

Time-resolved pump-probe measurements show ultrafast and heat accumulation demagnetization in Co/Pd superlattices on glass substrates. A model of demagnetizing fields and micromagnetic simulations are applied to examine the evolution of a demagnetized cylinder into a switched state.

[10]
Title: Ultracompact graphene-hBN amplitude modulator
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)

The hyperbolic phonon-polaritons within the Reststrahlen band of hBN is of great interest for applications in nanophotonics as they are capable of propagating light signal with low losses over large distances. However, due to the phononic nature of the polaritons in hBN, amplitude modulation of its signal proves to be difficult and has been underexplored. In this paper we propose a broadband efficient amplitude modulator for hyperbolic rays in hBN operating in the frequency range between 1450 cm$^{-1}$ and 1550 cm$^{-1}$. The modulating region comprises a few tens of nanometers wide gap carved within the hBN slab and covered by a graphene layer, where electrostatically gated graphene serves as a mediator that facilitates the coupling between phonon-polaritons on each side of the gap through plasmonic modes within graphene. We demonstrate that such an ultra compact modulator has insertion losses as low as 3 dB and provides modulation depth varying between 14 and 20 dB within the type-II hyperbolicity region of hBN.

[11]
Title: Time-reversal symmetry breaking phase and gapped surface states in d-wave nanoscale superconductors
Comments: 6 pages 4 figures, to be published in Journal of Physics: Conference Series (Proceedings of LT28, Gothenburg, Sweden, 9-16 Aug. 2017)
Subjects: Superconductivity (cond-mat.supr-con)

We solve the Bogoliubov-de Gennes equations self-consistently for d-wave superconductors with [110] surfaces. We find spontaneous breaking of time-reversal symmetry (TRS) caused by the spontaneous occurrence of a complex order parameter with an extended s-wave symmetry along the [110] surfaces. In the TRS-breaking phase, the d-wave order parameter itself becomes complex. We also show that vortex-antivortex pairs can appear along the [110] surfaces of nanoribbons. These pairs are detectable with surface sensitive probes.

[12]
Title: Entropy of random symbolic high-order bilinear Markov chains
Subjects: Statistical Mechanics (cond-mat.stat-mech); Data Analysis, Statistics and Probability (physics.data-an)

The main goal of this paper is to develop an estimate for the entropy of random stationary ergodic symbolic sequences with elements belonging to a finite alphabet. We present here the detailed analytical study of the entropy for the high-order Markov chain in the bilinear approximation. The appendix contains a short comprehensive introduction into the subject of study.

[13]
Title: The long-range spin-singlet proximity effect for the Josephson system with single-crystal ferromagnet due to its band structure features
Subjects: Superconductivity (cond-mat.supr-con)

The possible explanation of the long-range proximity effect observed in the single-crystalline cobalt nanowire sandwiched between two tungsten superconducting electrodes [Wang, M. \textit{et al}. \textit{ Nat. Phys}. \textbf{6}, 389 (2010)] is proposed. The theoretical approach is based on the features of band structure of a ferromagnet. To connect the exchange field with the momentum of quasiparticles the distinction between their effective masses in majority and minority spin bands and the Fermi surface anisotropy are taken into account. The derived Eilenberger-like equations allow to obtain the renormalized effective exchange interaction that can be completely compensated for some crystallographic direction under certain conditions. The proposed theoretical model is also compared with previous approaches.

[14]
Title: Unique Information via Dependency Constraints
Comments: 11 pages, 6 figures, 3 appendices; this http URL
Subjects: Statistical Mechanics (cond-mat.stat-mech); Information Theory (cs.IT); Learning (cs.LG); Statistics Theory (math.ST)

The partial information decomposition is perhaps the leading proposal for resolving shared information in a joint random variable into redundant, synergistic, and unique constituents. Unfortunately, the framework has been hindered by a lack of a generally agreed-upon, multivariate method of quantifying the constituents. Here, we take a step toward rectifying this by developing a decomposition based on a new method that quantifies unique information. The result is the first measure which satisfies the core axioms of the framework while also not treating identical but independent channels as redundant. This marks a key step forward in the practical application of the partial information decomposition.

[15]
Title: Phosphorous dimerization in GaP at high pressure
Subjects: Materials Science (cond-mat.mtrl-sci)

Using combined experimental and computational approaches we show that at 43 GPa and 1300 K gallium phosphide adopts the super-Cmcm structure, here indicated with its Pearson notation oS24. First-principles enthalpy calculations demonstrate that this oS24 structure is more thermodynamically stable above about 20 GPa than other proposed polymorphs, such as cubic ZB and SC16 or the ubiquitous orthorhombic Cmcm phase (oS8). It is found that oS24-structured GaP exhibits short P-P bonds, according to our high-resolution structural analysis. Such phosphorous dimerization in GaP, observed for the first time and confirmed by ab initio calculations, sheds light on the nature of the super-Cmcm structure and provides critical new insights into the high-pressure polymorphism of octet semiconductors. Bond directionality and anisotropy, in addition to 5-fold phosphorous coordination, explain the relatively low symmetry of this high-pressure structure.

[16]
Title: Microscopic Dynamics of Li$^{+}$ in Rutile TiO$_{2}$ Revealed by $^{8}$Li $β$-detected NMR
Subjects: Materials Science (cond-mat.mtrl-sci)

We report measurements of the dynamics of isolated $^{8}$Li$^{+}$ in single crystal rutile TiO$_{2}$ using $\beta$-detected NMR. From spin-lattice relaxation and motional narrowing, we find two sets of thermally activated dynamics: one below 100 K; and one at higher temperatures. At low temperature, the activation barrier is $26.8(6)$ meV with prefactor $1.23(5) \times 10^{10}$ s$^{-1}$. We suggest this is unrelated to Li$^{+}$ motion, and rather is a consequence of electron polarons in the vicinity of the implanted $^{8}$Li$^{+}$ that are known to become mobile in this temperature range. Above 100 K, Li$^{+}$ undergoes long-range diffusion as an isolated uncomplexed cation, characterized by an activation energy and prefactor of $0.32(2)$ eV and $1.0(5) \times 10^{16}$ s$^{-1}$, in agreement with macroscopic diffusion measurements. These results in the dilute limit from a microscopic probe indicate that Li$^{+}$ concentration does not limit the diffusivity even up to high concentrations, but that some key ingredient is missing in the calculations of the migration barrier. The anomalous prefactors provide further insight into both Li$^{+}$ and polaron motion.

[17]
Title: Phase-field modeling and electronic structural analysis of flexoelectric effect at 180° domain walls in ferroelectric PbTiO3
Subjects: Materials Science (cond-mat.mtrl-sci)

Flexoelectric effect is the coupling between strain, polarization and their gradients, which are prominent at the nanoscale. Although this effect is important to understand nanostructures, such as domain walls in ferroelectrics, its electronic mechanism is not clear. In this work, we combined phase-field simulations and first-principles calculations to study the 180{\deg} domain walls in tetragonal ferroelectric PbTiO3, and found that the ultimate source of N\'eel components is the gradient of the square of spontaneous polarizations. Electronic structural analysis reveals that there is a redistribution of electronic charge density and potential around domain walls, which produces the electric field and N\'eel components. This work thus sheds light on the electronic mechanism of the flexoelectric effect around 180{\deg} domain walls in tetragonal ferroelectrics.

[18]
Title: Many-body theory for proton-induced point-defect effects on losses of electron energy and photons in quantum wells
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)

The effects of point defects on the loss of either energies of ballistic electron beams or incident photons are studied by using a many-body theory in a multi-quantum-well system. This includes the defect-induced vertex correction to a bare polarization function of electrons within the ladder approximation as well as the intralayer and interlayer screening of defect-electron interactions are also taken into account in the random-phase approximation. The numerical results of defect effects on both energy-loss and optical-absorption spectra are presented and analyzed for various defect densities, number of quantum wells, and wave vectors. The diffusion-reaction equation is employed for calculating distributions of point defects in a layered structure. For completeness, the production rate for Frenkel-pair defects and their initial concentration are obtained based on atomic-level molecular-dynamics simulations. By combining defect-effect, diffusion-reaction and molecular-dynamics models proposed in this paper with a space-weather forecast model for the first time, it will be possible to enable specific designing for electronic and optoelectronic quantum devices that will be operated in space with radiation-hardening protection, and therefore, will effectively extend the lifetime of these satellite onboard electronic and optoelectronic devices.

[19]
Title: Path-Integral Isomorphic Hamiltonian for Including Nuclear Quantum Effects in Non-adiabatic Dynamics
Subjects: Statistical Mechanics (cond-mat.stat-mech)

We describe a path-integral approach for including nuclear quantum effects in non-adiabatic chemical dynamics simulations. For a general physical system with multiple electronic energy levels, a corresponding isomorphic Hamiltonian is introduced, such that Boltzmann sampling of the isomorphic Hamiltonian with classical nuclear degrees of freedom yields the exact quantum Boltzmann distribution for the original physical system. In the limit of a single electronic energy level, the isomorphic Hamiltonian reduces to the familiar cases of either ring polymer molecular dynamics (RPMD) or centroid molecular dynamics Hamiltonians, depending on implementation. An advantage of the isomorphic Hamiltonian is that it can easily be combined with existing mixed quantum-classical dynamics methods, such as surface hopping or Ehrenfest dynamics, to enable the simulation of electronically non-adiabatic processes with nuclear quantum effects. We present numerical applications of the isomorphic Hamiltonian to model two- and three-level systems, with encouraging results that include improvement upon a previously reported combination of RPMD with surface hopping in the deep-tunneling regime.

[20]
Title: Ponderous impurities in a Luttinger liquid
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)

In this work, analytical expressions for the Green function of a Luttinger liquid are dervied with one and two mobile impurities (heavy particles) using a combination of bosonization and perturbative approaches. The calculations are done in the random phase approximation (RPA) limit using the powerful non-chiral bosonization technique (NCBT) which is nothing but the resummation of the {\it{most singular parts}} of the RPA terms of the Green function expanded out in powers of the forward scattering between fermions {\it{with the source of inhomogeneities treated exactly}}. The force acting on the heavy particle(s) is studied as a function of its terminal velocity, both in the linear and non-linear regime. Linear mobility (which is valid for impurities moving much slower than a certain cross-over speed) has a power-law temperature dependence whose exponent has a closed algebraic expression in terms of the various parameters in the problem. This expression interpolates between the ballistic regime of no-coupling with the fermions and the no-tunneling regime. When the speed of the impurity is much larger than this cross-over speed, the applied force depends nonlinearly on the speed and this too is a power-law with a closely related exponent. The case of two mobile impurities is also studied whose mobility exhibits peculiar resonances when their mutual separation is appropriately chosen.

[21]
Title: Electronic signature of the vacancy ordering in NbO (Nb3O3)
Subjects: Materials Science (cond-mat.mtrl-sci)

We investigated the electronic structure of the vacancy-ordered 4d-transition metal monoxide NbO (Nb3O3) using angle-integrated soft- and hard-x-ray photoelectron spectroscopy as well as ultra-violet angle-resolved photoelectron spectroscopy. We found that density-functional-based band structure calculations can describe the spectral features accurately provided that self-interaction effects are taken into account. In the angle-resolved spectra we were able to identify the so-called vacancy band that characterizes the ordering of the vacancies. This together with the band structure results indicates the important role of the very large inter-Nb-4d hybridization for the formation of the ordered vacancies and the high thermal stability of the ordered structure of niobium monoxide.

[22]
Title: Efficient and controlled domain wall nucleation for magnetic shift registers
Journal-ref: Scientific Reports, 7, 11909 (2017)
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)

Ultrathin ferromagnetic strips with high perpendicular anisotropy have been proposed for the development of memory devices where the information is coded in tiny domains separated by domain walls. The design of practical devices requires creating, manipulating and detecting domain walls in ferromagnetic strips. Recent observations have shown highly efficient current-driven domain wall dynamics in multilayers lacking structural symmetry, where the walls adopt a chiral structure and can be driven at high velocities. However, putting such a device into practice requires the continuous and synchronous injection of domain walls as the first step. Here, we propose and demonstrate an efficient and simple scheme for nucleating domain walls using the symmetry of the spin orbit torques. Trains of short sub-nanosecond current pulses are injected in a double bit line to generate a localized longitudinal Oersted field in the ferromagnetic strip. Simultaneously, other current pulses are injected through the heavy metal under the ferromagnetic strip. Notably, the Slonczewski-like spin orbit torque assisted by the Oersted field allows the controlled injection of a series of domain walls, giving rise to a controlled manner for writing binary information and, consequently, to the design of a simple and efficient domain wall shift register.

[23]
Title: How To Identify Plasmons from the Optical Response of Nanostructures
Comments: This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes. Link to th original article: this http URL
Journal-ref: ACS Nano, 2017, 11 (7), pp 7321-7335
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)

A promising trend in plasmonics involves shrinking the size of plasmon-supporting structures down to a few nanometers, thus enabling control over light-matter interaction at extreme-subwavelength scales. In this limit, quantum mechanical effects, such as nonlocal screening and size quantization, strongly affect the plasmonic response, rendering it substantially different from classical predictions. For very small clusters and molecules, collective plasmonic modes are hard to distinguish from other excitations such as single-electron transitions. Using rigorous quantum mechanical computational techniques for a wide variety of physical systems, we describe how an optical resonance of a nanostructure can be classified as either plasmonic or nonplasmonic. More precisely, we define a universal metric for such classification, the generalized plasmonicity index (GPI), which can be straightforwardly implemented in any computational electronic-structure method or classical electromagnetic approach to discriminate plasmons from single-particle excitations and photonic modes. Using the GPI, we investigate the plasmonicity of optical resonances in a wide range of systems including: the emergence of plasmonic behavior in small jellium spheres as the size and the number of electrons increase; atomic-scale metallic clusters as a function of the number of atoms; and nanostructured graphene as a function of size and doping down to the molecular plasmons in polycyclic aromatic hydrocarbons. Our study provides a rigorous foundation for the further development of ultrasmall nanostructures based on molecular plasmonics

[24]
Title: Symmetry-Adapted Machine-Learning for Tensorial Properties of Atomistic Systems
Subjects: Materials Science (cond-mat.mtrl-sci); Statistical Mechanics (cond-mat.stat-mech)

Statistical learning methods show great promise in providing an accurate prediction of materials and molecular properties, while minimizing the need for computationally demanding electronic structure calculations. The accuracy and transferability of these models are increased significantly by encoding into the learning procedure the fundamental symmetries of rotational and permutational invariance of scalar properties. However, the prediction of tensorial properties requires that the model respects the appropriate geometric transformations, rather than invariance, when the reference frame is rotated. We introduce a formalism that can be used to perform machine-learning of tensorial properties of arbitrary rank for general molecular geometries. To demonstrate it, we derive a tensor kernel adapted to rotational symmetry, which is the natural generalization of the smooth overlap of atomic positions (SOAP) kernel commonly used for the prediction of scalar properties at the atomic scale. The performance and generality of the approach is demonstrated by learning the instantaneous electrical response of water oligomers of increasing complexity, from the isolated molecule to the condensed phase.

[25]
Title: Rational design and dynamics of self-propelled colloidal bead chains: from rotators to flagella
Subjects: Soft Condensed Matter (cond-mat.soft)

The quest for designing new self-propelled colloids is fuelled by the demand for simple experimental models to study the collective behaviour of their more complex natural counterparts. Most synthetic self-propelled particles move by converting the input energy into translational motion. In this work we address the question if simple self-propelled spheres can assemble into more complex structures that exhibit rotational motion, possibly coupled with translational motion as in flagella. We exploit a combination of induced dipolar interactions and a bonding step to create permanent linear bead chains, composed of self-propelled Janus spheres, with a well-controlled internal structure. Next, we study how flexibility between individual swimmers in a chain can affect its swimming behaviour. Permanent rigid chains showed only active rotational or spinning motion, whereas longer semi-flexible chains showed both translational and rotational motion resembling flagella like-motion, in the presence of the fuel. Moreover, we are able to reproduce our experimental results using numerical calculations with a minimal model, which includes full hydrodynamic interactions with the fluid. Our method is general and opens a new way to design novel self-propelled colloids with complex swimming behaviours, using different complex starting building blocks in combination with the flexibility between them.

[26]
Title: Rayleigh-Taylor instability in soft elastic layers
Journal-ref: Phil. Trans. R. Soc. A 375.2093 (2017): 20160421
Subjects: Soft Condensed Matter (cond-mat.soft)

This work investigates the morphological stability of a soft body composed of two heavy elastic layers, attached to a rigid surface and subjected only to the bulk gravity force. Using theoretical and computational tools, we characterize the selection of different patterns as well as their nonlinear evolution, unveiling the interplay between elastic and geometric effects for their formation.
Unlike similar gravity-induced shape transitions in fluids, as the Rayleigh-Taylor instability, we prove that the nonlinear elastic effects saturate the dynamic instability of the bifurcated solutions, displaying a rich morphological diagram where both digitations and stable wrinkling can emerge. The results of this work provide important guidelines for the design of novel soft systems with tunable shapes, with several applications in engineering sciences.

[27]
Title: Thermodynamic investigations on the growth of CuAlO$_2$ delafossite crystals
Subjects: Materials Science (cond-mat.mtrl-sci)

Simultaneous differential thermal analysis (DTA) and thermogravimetric (TG) measurements with copper oxide/aluminum oxide mixtures were performed in atmospheres with varying oxygen partial pressures and with crucibles made of different materials. Only sapphire and platinum crucibles proved to be stable under conditions that are useful for the growth of CuAlO$_2$ delafossite single crystals. Then the ternary phase diagram Al$_2$O$_3$-CuO-Cu and its isopleth section Cu$_2$O-Al$_2$O$_3$ were redetermined. Millimeter sized crystals could be obtained from copper oxide melts with 1-2 mol % addition of aluminum oxide that are stable in platinum crucibles held in oxidizing atmosphere containing 15-21 % oxygen.

[28]
Title: Vibrational effects in x-ray absorption (XAS) and resonant inelastic x-ray scattering (RIXS) using a semiclassical scheme
Subjects: Materials Science (cond-mat.mtrl-sci)

A new method is presented for describing vibrational effects in x-ray absorption spectroscopy (XAS) and resonant inelastic x-ray scattering (RIXS) using a combination of the classical Franck-Condon (FC) approximation and classical trajectories run on the core-excited state. The formulation of RIXS is an extension of the semiclassical Kramers-Heisenberg (SCKH) formalism of Ref. {Ljungberg_2010} to the resonant case, retaining approximately the same computational cost. To overcome difficulties with connecting the absorption and emission processes in RIXS the classical FC approximation is used for the absorption, which is seen to work well provided that a zero-point-energy correction is included.
In the case of core-excited states with dissociative character the method is capable of closely reproducing the main features for one-dimensional test systems, compared to the quantum mechanical formulation. Due to the good accuracy combined with the relatively low computational cost, the method has large potential of being used for complex systems with many degrees of freedom, such as liquids and surface adsorbates.

[29]
Title: Topological semimetals induced by magnetic control of the Luttinger q-term in pyrochlore iridates
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Materials Science (cond-mat.mtrl-sci); Strongly Correlated Electrons (cond-mat.str-el)

Pyrochlore iridate antiferromagnet is the first material in which Weyl fermions are predicted to exist in condensed matters. Although several promising experimental results, which may be originated from Weyl fermions, have been reported, an unambiguous proof for the presence of the Weyl semimetal in this system has not been achieved yet. The accumulated theoretical and experimental knowledge consistently shows that the Weyl semimetal can, in principle, be realized in this system but only within a very narrow window in the parameter space, which makes it difficult to access the relevant state in experiment. In this work, we theoretically propose that applying magnetic field is a promising way to realize the Weyl semimetal phase in pyrochlore iridates since magnetic field not only can expand the range in which the Weyl semimetal phase exists but also can create new topological semimetal phases across additional band inversion. Here the central role is played by the presence of a quadratic band crossing with four-fold degeneracy in the paramagnetic band structure that exists before the time-reversal symmetry is broken. Due to the large degeneracy at the crossing point and the strong spin-orbit coupling, the degenerate states at the crossing point can show the anisotropic Zeeman effect, which can be described by the so-called q-term in the Luttinger Hamiltonian, as well as the conventional isotropic Zeeman effect. Moreover, the relative magnitude of these two different Zeeman terms can be controlled by varying the orientation of the four spins within the unit cell, which, in turn, manipulates the topological property of the iridium band structure. Such an intriguing behavior occurs due to the fact that the unit cell is composed of a cluster of four spins in a tetrahedron whose magnetic mulipole moments can be continuously tuned by varying the spin orientation within the unit cell.

[30]
Title: Dynamics and transverse relaxation of an unconventional spin-rotation mode in a two-dimensional strongly magnetized electron gas
Authors: S. Dickmann
Comments: 11 pages including a figure
Subjects: Strongly Correlated Electrons (cond-mat.str-el)

An unconventional spin-rotation mode emerging in a quantum Hall ferromagnet due to excitation by a laser pulse is studied. This state, macroscopically representing a rotation of the entire electron spin-system to a certain angle, microscopically is not equivalent to a coherent turn of all spins as a single-whole and is presented in the form of a combination of eigen quantum states corresponding to all possible S_z spin numbers. Motion of the macroscopic quantum state is studied microscopically by solving a non-stationary Schroedinger equation and by means of a kinetic approach where damping of the spin-rotation mode is related to an elementary process - transformation of a 'Goldstone spin exciton' to a 'spin-wave exciton'. The system exhibits a spin stochastization mechanism (determined by spatial fluctuations of the g-factor) providing the damping - the transverse spin relaxation, but irrelevant to a decay of spin-wave excitons and thus not providing the longitudinal relaxation - recovery of the S_z number to its equilibrium value.

[31]
Title: Thermodynamical consistency of the Dual Phase Lag heat conduction equation
Subjects: Statistical Mechanics (cond-mat.stat-mech)

Dual phase lag equation for heat conduction is analyzed from the point of view of non-equilibrium thermodynamics. Its first order Taylor series expansion is consistent with the second law as long as the two relaxation times are not negative.

[32]
Title: Time-dependent reflection at the localization transition
Subjects: Disordered Systems and Neural Networks (cond-mat.dis-nn)

A short quasi-monochromatic wave packet incident on a semi-infinite disordered medium gives rise to a reflected wave. The intensity of the latter decays as a power law $1/t^{\alpha}$ in the long-time limit. Using the one-dimensional Aubry-Andr\'{e} model, we show that at the critical point of Anderson localization transition the decay can be as slow as $1/t^{1 + \varepsilon}$ with $\varepsilon \ll 1$ when the central energy of the wave packet falls inside a spectral gap of the disordered system. This is the slowest decay that is physically possible, slower than both $1/t^2$ found in the Anderson localization regime and $1/t^{3/2}$ expected for a one-dimensional random walk of classical particles.

[33]
Title: Evolution of ground state wave function in CeCoIn$_5$ upon Cd or Sn doping
Subjects: Strongly Correlated Electrons (cond-mat.str-el)

We present linear polarization-dependent soft x-ray absorption spectroscopy data at the Ce $M_{4,5}$ edges of Cd and Sn doped CeCoIn$_5$. The 4$f$ ground state wave functions have been determined for their superconducting, antiferromagnetic and paramagnetic ground states. The absence of changes in the wave functions in CeCo(In$_{1-x}$Cd$_x$)$_5$ suggests the 4$f$\,--\,conduction electron ($cf$) hybridization is not affected by globally Cd doping, thus supporting the interpretation of magnetic droplets nucleating long range magnetic order. This is contrasted by changes in the wave function due to Sn substitution. Increasing Sn in CeCo(In$_{1-y}$Sn$_y$)$_5$ compresses the 4$f$ orbitals into the tetragonal plane of these materials, suggesting enhanced $cf$ hybridization with the in-plane In(1) atoms and a homogeneous altering of the electronic structure. As these experiments show, the 4$f$ wave functions are a very sensitive probe of small changes in the hybridization of 4$f$ and conduction electrons, even conveying information about direction dependencies.

[34]
Title: Single-bubble and multi-bubble cavitation in water triggered by Laser-driven focusing shock waves
Subjects: Soft Condensed Matter (cond-mat.soft)

In this study a single laser pulse spatially shaped into a ring is focused into a thin water layer, creating an annular cavitation bubble and cylindrical shock waves: an outer shock that diverges away from the excitation laser ring and an inner shock that focuses towards the center. A few nanoseconds after the converging shock reaches the focus and diverges away from the center, a single bubble nucleates at the center. The inner diverging shock then reaches the surface of the annular laser-induced bubble and reflects at the boundary, initiating nucleation of a tertiary bubble cloud. In the present experiments, we have performed time-resolved imaging of shock propagation and bubble wall motion. Our experimental observations of single-bubble cavitation and collapse and appearance of ring-shaped bubble clouds are consistent with our numerical simulations that solve a one dimensional Euler equation in cylindrical coordinates. The numerical results agree qualitatively with the experimental observations of the appearance and growth of dense ring-shaped bubble clouds at the smallest laser excitation rings. Our technique of shock-driven bubble cavitation opens novel perspectives for the investigation of shock-induced single-bubble or multi-bubble sonoluminescence phenomena in thin liquids.

[35]
Title: Electron-phonon interaction and transport properties of metallic bulk and monolayer transition metal dichalcogenide TaS$_2$
Comments: accepted in IOPscience 2D Materials, supplemental material is available on the publishers page
Subjects: Materials Science (cond-mat.mtrl-sci)

Transition metal dichalcogenides have recently emerged as promising two-dimensional materials with intriguing electronic properties. Existing calculations of intrinsic phonon-limited electronic transport so far have concentrated on the semicondcucting members of this family. In this paper we extend these studies by investigating the influence of electron-phonon coupling on the electronic transport properties and band renormalization of prototype inherent metallic bulk and monolayer TaS$_2$. Based on density functional perturbation theory and semi-classical Boltzmann transport calculations, promising room temperature mobilities and sheet conductances are found, which can compete with other established 2D materials, leaving TaS$_2$ as promising material candidate for transparent conductors or as atomically thin interconnects. Throughout the paper, the electronic and transport properties of TaS$_2$ are compared to those of its isoelectronic counterpart TaSe$_2$ and additional informations to the latter are given. We furthermore comment on the conventional su- perconductivity in TaS$_2$, where no phonon-mediated enhancement of TC in the monolayer compared to the bulk state was found.

[36]
Title: ScPd2Al3 New Polymorphic Phase in Al-Pd-Sc System
Journal-ref: Solid State Communications 268, 12-14 (2017)
Subjects: Materials Science (cond-mat.mtrl-sci)

We have discovered a new compound of the composition ScPd2Al3 crystallizing in unknown structure type. Moreover, ScPd2Al3 reveals polymorphism. We have found an orthorhombic crystal structure at room temperature and a high temperature cubic phase. The polymorphic phases are separated by a reversible first order transition at 1053{\deg}C with a hysteresis of 19{\deg}C. ScPd2Al3 exists as a very stable intermetallic phase just in the vicinity of the icosahedral quasicrystal Tsai-type i-phase Al54Pd30Sc16.

[37]
Title: Steady Microfluidic Measurements of Mutual Diffusion Coefficients of Liquid Binary Mixtures
Subjects: Soft Condensed Matter (cond-mat.soft)

We present a microfluidic method leading to accurate measurements of the mutual diffusion coefficient of a liquid binary mixture over the whole solute concentration range in a single experiment. This method fully exploits solvent pervaporation through a poly(dimethylsiloxane) (PDMS) membrane to obtain a steady concentration gradient within a microfluidic channel. Our method is applicable for solutes which cannot permeate through PDMS, and requires the activity and the density over the full concentration range as input parameters. We demonstrate the accuracy of our methodology by measuring the mutual diffusion coefficient of the water (1) $+$ glycerol (2) mixture, from measurements of the concentration gradient using Raman confocal spectroscopy and the pervaporation-induced flow using particle tracking velocimetry.

[38]
Title: Magnetic ground state of the Ising-like antiferromagnet DyScO$_3$
Comments: 9 pages and 6 figures; to be published in Phys. Rev. B
Subjects: Strongly Correlated Electrons (cond-mat.str-el)

We report the low temperature magnetic properties of the DyScO$_3$ perovskite, which were characterized by means of single crystal and powder neutron scattering, and by magnetization measurements. Below $T_{\mathrm{N}}=3.15$ K, Dy$^{3+}$ moments form an antiferromagnetic structure with an easy axis of magnetization lying in the $ab$-plane. The magnetic moments are inclined at an angle of $\sim\pm{28}^{\circ}$ to the $b$-axis. We show that the ground state Kramers doublet of Dy$^{3+}$ is made up of primarily $|\pm 15/2\rangle$ eigenvectors and well separated by crystal field from the first excited state at $E_1=24.9$ meV. This leads to an extreme Ising single-ion anisotropy, $M_{\perp}/M_{\|}\sim{0.05}$. The transverse magnetic fluctuations, which are proportional to $M^{2}_{\perp}/M^{2}_{\|}$, are suppressed and only moment fluctuations along the local Ising direction are allowed. We also found that the Dy-Dy dipolar interactions along the crystallographic $c$-axis are 2-4 times larger than in-plane interactions.

[39]
Title: Photoinduced vibronic coupling in two-level dissipative systems
Authors: Andrei Ivanov
Comments: Reference 22 is the unpublished article which is submitted to arXiv
Subjects: Other Condensed Matter (cond-mat.other); Optics (physics.optics)

Interaction of an electron system with a strong electromagnetic wave leads to rearrangement both the electron and vibrational energy spectra of a dissipative system. For instance, the optically coupled electron levels become split in the conditions of the ac Stark effect that gives rise to appearance of the nonadiabatic coupling between the electron and vibrational motions. The nonadiabatic coupling exerts a substantial impact on the electron and phonon dynamics and must be taken into account to determine the system wave functions. In this paper, the vibronic coupling induced by the ac Stark effect is considered. It is shown that the interaction between the electron states dressed by an electromagnetic field and the forced vibrations of reservoir oscillators under the action of rapid changing of the electron density with the Rabi frequency is responsible for establishment of the photoinduced vibronic coupling. However, if the resonance conditions for the optical phonon frequency and the transition frequency of electrons in the dressed state basis are satisfied, the vibronic coupling is due to the electron-phonon interaction. Additionally, photoinduced vibronic coupling results in appearance of the doubly dressed states which are formed by both the electron-photon and electron-vibrational interactions.

[40]
Title: Energy Transfer Controlled by Dynamical Stark Shift in Two-level Dissipative Systems
Authors: Andrei Ivanov
Comments: Reference 16 is the unpublished article which is submitted to arXiv
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Optics (physics.optics); Quantum Physics (quant-ph)

A strong electromagnetic field interacting with an electron system generates both the Rabi oscillations and the Stark splitting of the electron density. Changing of the electron density gives rise to nonadiabatic effects due to existence of the electron-vibrational interaction in a dissipative system. In this Letter, the mechanism of energy transfer between the electron system and the phonon reservoir is presented. This mechanism is based on establishment of the coupling between the electron states dressed by the electromagnetic field and the forced vibrations of reservoir oscillators under the action of rapid changing of the electron density with the Rabi frequency. The photoinduced vibronic coupling results in appearance of the states that are doubly dressed by interaction, first time due to the electron-photon interaction, and second time due to the electron-vibrational interaction. Moreover, this coupling opens the way to control energy which can be transferred to (heating) or removed from (cooling) the phonon reservoir depending on the parameters of the electromagnetic pulse.

[41]
Title: Chiral symmetry classes and Dirac nodal lines in three-dimensional layered systems
Comments: 5 pages and 2 figures
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)

We study the existence and stability of Dirac nodal lines in three-dimensional layered systems, whose layers individually have Dirac nodal points protected by chiral (sublattice) symmetry. The model system we consider is the rhombohedral stack of graphene layers with each layer subjected to a uniform external potential that respects either AIII or BDI classes. From the Hamiltonians in either classes, a pair of nontrivial spiraling Dirac nodal lines can be derived. The results are reasonable in accord to the topological classification of gapless phases for codimension $2$. The nodal lines approach each other as the magnitude of the potential increases, revealing their annihilation due to the fact that regarding the full system their topological invariants are cancelled out.

[42]
Title: A quantum model for voltage noise: Theory and Experiments
Authors: J. I. Izpura
Comments: 15 pages with two embedded figures showing how two-terminal devices interact with their thermal bath to show voltage noise
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)

Although the Fluctuation-Dissipation framework is a first step to get a quantum model for electrical noise, the merging of displacement and conduction currents into the sole current of a series notion like the resistance R(f) does not help in it this task. Used to handle these currents as orthogonal components in electromagnetic waves, the usage of the impedance Z(jf)=R(f)+jX(f) for the noisy device hides the way it interacts with its thermal bath. In contrast to this, the admittance Y(jf) is a parallel notion directly linked with the aforementioned interaction that has led us to develop a discrete model for current fluctuations where single electrons randomly shuttling between any pair of terminals generate the voltage noise we can measure between them.

[43]
Title: Majorana fermions in three dimensions and realization in critical Weyl semimetals
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); High Energy Physics - Theory (hep-th)

We present two band models for free fermion with charge conjugation symmetry in three dimensions. Without time reversal symmetry (TRS), the weak pairing gapless $A$-phase is a Majorana fermion $p_x+ip_y$ wave FFLO state while the strong pairing gapped $B$-phase belongs to topologically trivial Class $D$. With TRS, there is a Majorana fermion $B$-phase belonging to Class $DIII$ with a non-zero Hopf invariant. The TRS $A$-phase is also a Majorana fermion FFLO state with TRS. The surface states of the TRS $B$-phase are either a valley-momentum locked Majorana-Dirac cone or a linear-quadratic mixed cone for a specific surface. The surface states of the $A$-phase on one surface are topologically nontrivial, either having $\mathbb{Z}$ or $\mathbb{Z}_2$ invariant depending on whether the system is TRS or not. The edge states of that surface are gapless Majorana modes. The Majorana fermion gapless FFLO states can be realized in critical Weyl semimetals (WSM) in which dual single Weyl nodes form dipoles and are nearly annihilated. The gapped $B$-phase emerges when Weyl node dipoles are about to be created. The WSM TaAs-family, a type-II WSM series Mo$_x$W$_{1-x}$Te$_2$-family, possible WSM La/LuBi$_{1-x}$ Sb$_x$Te$_3$ and topological crystalline insulators Sn$_{1-x}$Pb$_x$(Te,Se) are candidates to be manipulated into these critical states based on Majorana fermion models.

[44]
Title: Possible multigap Type-I superconductivity in the layered Boride RuB$_2$
Subjects: Superconductivity (cond-mat.supr-con); Materials Science (cond-mat.mtrl-sci); Strongly Correlated Electrons (cond-mat.str-el)

The structure of the layered transition-metal Borides $A$B$_2$ ($A =$ Os, Ru) is built up by alternating $T$ and B layers with the B layers forming a puckered honeycomb. Here we report superconducting properties of RuB$_2$ with a $T_c \approx 1.5$K using measurements of the magnetic susceptibility versus temperature $T$, magnetization $M$ versus magnetic field $H$, resistivity versus $T$, and heat capacity versus $T$ at various $H$. We observe a reduced heat capacity anomaly at $T_c$ given by $\Delta C/\gamma T_c \approx 1.1$ suggesting multi-gap superconductivity. Strong support for this is obtained by the successful fitting of the electronic specific heat data to a two-gap model with gap values $\Delta_1/k_BT_c \approx 1.88$ and $\Delta_2/k_BT_c \approx 1.13$. Additionally, $M$ versus $H$ measurements reveal a behaviour consistent with Type-I superconductivity. This is confirmed by estimates of the Ginzburg-Landau parameter $\kappa \approx 0.1$--$0.66$. These results strongly suggest multi-gap Type-I superconductivity in RuB$_2$. We also calculate the band structure and obtain the Fermi surface for RuB$_2$. The Fermi surface consists of one quasi-two-dimensional sheet and two nested ellipsoidal sheets very similar to OsB$_2$. An additional small $4^{\rm th}$ sheet is also found for RuB$_2$. RuB$_2$ could thus be a rare example of a multi-gap Type-I superconductor.

[45]
Title: Correlative Microscopy of Morphology and Luminescence of Cu porphyrin aggregates
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Soft Condensed Matter (cond-mat.soft); Chemical Physics (physics.chem-ph)

Transfer of energy and information through molecule aggregates requires as one important building block anisotropic, cable-like structures. Knowledge on the spatial correlation of luminescence and morphology represents a prerequisite in the understanding of internal processes and will be important for architecting suitable landscapes. In this context we study the morphology, fluorescence and phosphorescence of molecule aggregate structures on surfaces in a spatially correlative way. We consider as two morphologies, lengthy strands and isotropic islands. It turns out that phosphorescence is quite strong compared to fluorescence and the spatial variation of the observed intensities is largely in line with the amount of dye. However in proportion, the strands exhibit more fluorescence than the isotropic islands suggesting weaker non-radiative channels. The ratio fluorescence to phosphorescence appears to be correlated with the degree of aggregation or internal order. The heights at which luminescence saturates is explained in the context of attenuation and emission multireflection, inside the dye. This is supported by correlative photoemission electron microscopy which is more sensitive to the surface region. The lengthy structures exhibit a pronounced polarization dependence of the luminescence with a relative dichroism up to about 60%, revealing substantial perpendicular orientation preference of the molecules with respect to the substrate and parallel with respect to the strands.

[46]
Title: Granular Response to Impact: Topology of the Force Networks
Subjects: Soft Condensed Matter (cond-mat.soft)

Impact of an intruder on granular matter leads to formation of mesoscopic force networks seen particularly clearly in the recent experiments carried out with photoelastic particles, e.g., Clark et al., Phys. Rev. Lett., 114 144502 (2015). These force networks are characterized by complex structure and evolve on fast time scales. While it is known that total photoelastic activity in the granular system is correlated with the acceleration of the intruder, it is not known how the structure of the force network evolves during impact, and if there is a dominant features in the networks that can be used to describe intruder's dynamics. Here, we use topological tools, in particular persistent homology, to describe these features. Persistent homology allows quantification of both structure and time evolution of the resulting force networks. We find that there is a clear correlation of the intruder's dynamics and some of the topological measures implemented. This finding allows us to discuss which properties of the force networks are most important when attempting to describe intruder's dynamics. Regarding temporal evolution of the networks, we are able to define the upper bound on the relevant time scale on which the networks evolve.

[47]
Title: Synchronization in Kuramoto-Sakaguchi ensembles with competing influence of common noise and global coupling
Comments: 27 pages, 5 figures, in Russian
Subjects: Statistical Mechanics (cond-mat.stat-mech); Adaptation and Self-Organizing Systems (nlin.AO)

We study the effects of synchronization and desynchronization in ensembles of phase oscillators with the global Kuramoto-Sakaguchi coupling under common noise driving. Since the mechanisms of synchronization by coupling and by common noise are essentially different, their interplay is of interest. In the thermodynamic limit of large number of oscillators, employing the Ott-Antonsen approach, we derive stochastic equations for the order parameters and consider their dynamics for two cases: (i) identical oscillators and (ii) small natural frequency mismatch. For identical oscillators, the stability of the perfect synchrony state is studied; a strong enough common noise is revealed to prevail over a moderate negative (repelling) coupling and to synchronize the ensemble. An inequality between the states of maximal asynchrony (zero-value of the order parameter) and perfect synchrony; the former can be only weakly stable, while the latter can become adsorbing (the transition to the synchrony becomes unidirectional). The dependence of the temporal dynamics of the transition on the system parameters is investigated. For nonidentical oscillators the perfect synchrony state becomes impossible and an absorbing state disappears; on its place, only a weakly stable state of imperfect synchrony remains. A nontrivial effect of the divergence of individual frequencies of oscillators with different natural frequencies is revealed and studied for moderate repelling coupling; meanwhile, the order parameter remains non-small for this case.

[48]
Title: A computational study of hafnia-based ferroelectric memories: from ab initio via physical modeling to circuit models of ferroelectric device
Subjects: Materials Science (cond-mat.mtrl-sci); Computational Physics (physics.comp-ph)

The discovery of ferroelectric properties of binary oxides revitalized the interest in ferroelectrics and bridged the scaling gap between the state-of-the-art semiconductor technology and ferroelectric memories. However, before hitting the markets, the origin of ferroelectricity and in-depth studies of device characteristics are needed. Establishing a correlation between the performance of the device and underlying physical mechanisms is the first step toward understanding the device and engineering guidelines for a novel, superior device. Therefore, in this paper a holistic modeling approaches which lead to a better understanding of ferroelectric memories based on hafnium and zirconium oxide is addressed. Starting from describing the stabilization of the ferroelectric phase within the binary oxides via physical modeling the physical mechanisms of the ferroelectric devices are reviewed. Besides, limitations and modeling of the multilevel operation and switching kinetics of ultimately scaled devices as well as the necessity for Landau-Khalatnikov approach are discussed. Furthermore, a device-level model of ferroelectric memory devices that can be used to study the array implementation and their operational schemes are addressed. Finally, a circuit model of the ferroelectric memory device is presented and potential further applications of ferroelectric devices are outlined.

### Cross-lists for Thu, 21 Sep 17

[49]  arXiv:1709.06621 (cross-list from math-ph) [pdf, ps, other]
Title: Localization in the Disordered Holstein model
Subjects: Mathematical Physics (math-ph); Disordered Systems and Neural Networks (cond-mat.dis-nn); Spectral Theory (math.SP)

The Holstein model describes the motion of a tight-binding tracer particle interacting with a field of quantum harmonic oscillators. We consider this model with an on-site random potential. Provided the hopping amplitude for the particle is small, we prove localization for matrix elements of the resolvent, in particle position and in the field Fock space. These bounds imply a form of dynamical localization for the particle position that leaves open the possibility of resonant tunneling in Fock space between equivalent field configurations.

[50]  arXiv:1709.06720 (cross-list from q-bio.QM) [pdf]
Title: SIRT6 Knockout Cells Resist Apoptosis Initiation but Not Progression: A Computational Method to Evaluate the Progression of Apoptosis
Subjects: Quantitative Methods (q-bio.QM); Statistical Mechanics (cond-mat.stat-mech); Cell Behavior (q-bio.CB)

Apoptosis is essential for numerous processes, such as development, resistance to infections, and suppression of tumorigenesis. Here, we investigate the influence of the nutrient sensing and longevity-assuring enzyme SIRT6 on the dynamics of apoptosis triggered by serum starvation. Specifically, we characterize the progression of apoptosis in wild type and SIRT6 deficient mouse embryonic fibroblasts using time-lapse flow cytometry and computational modelling based on rate-equations and cell distribution analysis. We find that SIRT6 deficient cells resist apoptosis by delaying its initiation. Interestingly, once apoptosis is initiated, the rate of its progression is higher in SIRT6 null cells compared to identically cultured wild type cells. However, SIRT6 null cells succumb to apoptosis more slowly, not only in response to nutrient deprivation but also in response to other stresses. Our data suggest that SIRT6 plays a role in several distinct steps of apoptosis. Overall, we demonstrate the utility of our computational model to describe stages of apoptosis progression and the integrity of the cellular membrane. Such measurements will be useful in a broad range of biological applications. We describe a computational method to evaluate the progression of apoptosis through different stages. Using this method, we describe how cells devoid of SIRT6 longevity gene respond to apoptosis stimuli, specifically, how they respond to starvation. We find that SIRT6 cells resist apoptosis initiation; however, once initiated, they progress through the apoptosis at a faster rate. These data are first of the kind and suggest that SIRT6 activities might play different roles at different stages of apoptosis. The model that we propose can be used to quantitatively evaluate progression of apoptosis and will be useful in studies of cancer treatments and other areas where apoptosis is involved.

[51]  arXiv:1709.06766 (cross-list from hep-th) [pdf, other]
Title: On actions for (entangling) surfaces and DCFTs
Subjects: High Energy Physics - Theory (hep-th); Soft Condensed Matter (cond-mat.soft); General Relativity and Quantum Cosmology (gr-qc); Mathematical Physics (math-ph)

The dynamics of surfaces and interfaces describe many physical systems, including fluid membranes, entanglement entropy and the coupling of defects to quantum field theories. Based on the formulation of submanifold calculus developed by Carter, we introduce a new variational principle for (entangling) surfaces. This principle captures all diffeomorphism constraints on surface/interface actions and their associated spacetime stress tensor. The different couplings to the geometric tensors appearing in the surface action are interpreted in terms of linear response coefficients within elasticity theory. An example of a surface action with edges at the two-derivative level is studied, including both the parity-even and parity-odd sectors. Its conformally invariant counterpart restricts the type of conformal anomalies that can appear in two-dimensional submanifolds with boundaries. Analogously to hydrodynamics, it is shown that classification methods can be used to constrain the stress tensor of (entangling) surfaces at a given order in derivatives. This analysis reveals a purely geometric parity-odd contribution to the Young modulus of a thin elastic membrane. Extending this novel variational principle to BCFTs and DCFTs in curved spacetimes allows to obtain the Ward identities for diffeomorphism and Weyl transformations. In this context, we provide a formal derivation of the contact terms in the stress tensor and of the displacement operator for a broad class of actions.

[52]  arXiv:1709.06920 (cross-list from quant-ph) [pdf, other]
Title: Uncertainty relations in implementation of unitary control
Subjects: Quantum Physics (quant-ph); Statistical Mechanics (cond-mat.stat-mech)

We study the underlying mechanism in the implementation of unitary control on a system with an experimental apparatus. We regard the unitary time-evolution in the system as a physical phenomenon that results from the interaction between the system and the apparatus. We model this situation using the setup of the system and an external system that represents the apparatus. We consider the conditions required to approximate the dynamics of the reduced density matrix of the system by the desired unitary time-evolution. Then, we derive fundamental trade-off relations to implement the unitary dynamics. The results show that achieving perfect unitary control in the system and eliminating the quantum fluctuation of energy in the external system are incompatible.

[53]  arXiv:1709.06944 (cross-list from physics.app-ph) [pdf, other]
Title: Optimizing Thermochromism of Solution-Processed VO$_2$ Nanocomposite Films for Chromogenic Fenestration
Authors: Joel P. Abraham
Subjects: Applied Physics (physics.app-ph); Materials Science (cond-mat.mtrl-sci)

Vanadium (IV) oxide is one of the most promising materials for thermochromic films due to its unique, reversible crystal phase transition from monoclinic (M1) to rutile (R) at its critical temperature (T$_c$) which corresponds to a change in optical properties: above T$_c$, VO$_2$ films exhibit a decreased transmittance for wavelengths of light in the near-infrared region. However, a high transmittance modulation often sacrifices luminous transmittance which is necessary for commercial and residential applications of this technology. In this study, we explore the potential for synthesis of VO$_2$ films in a matrix of metal oxide nanocrystals, using In$_2$O$_3$, TiO$_2$, and ZnO as diluents. We seek to optimize the annealing conditions to yield desirable optical properties. Although the films diluted with TiO$_2$ and ZnO failed to show transmittance modulation, those diluted with In$_2$O$_3$ exhibited strong thermochromism. Our investigation introduces a novel window film consisting of a 0.93 metal ionic molar ratio VO$_2$-In$_2$O$_3$ nanocrystalline matrix, demonstrating a significant increase in luminous transmittance without any measurable impact on thermochromic character. Furthermore, solution-processing mitigates costs, allowing this film to be synthesized 4x-7x cheaper than industry standards. This study represents a crucial development in film chemistry and paves the way for further application of VO$_2$ nanocomposite films in chromogenic fenestration.

[54]  arXiv:1709.06950 (cross-list from q-bio.NC) [pdf, ps, other]
Title: Spatial features of synaptic adaptation affecting learning performance
Journal-ref: Scientific Reports 7, 11016 (2017)
Subjects: Neurons and Cognition (q-bio.NC); Disordered Systems and Neural Networks (cond-mat.dis-nn); Learning (cs.LG); Neural and Evolutionary Computing (cs.NE)

Recent studies have proposed that the diffusion of messenger molecules, such as monoamines, can mediate the plastic adaptation of synapses in supervised learning of neural networks. Based on these findings we developed a model for neural learning, where the signal for plastic adaptation is assumed to propagate through the extracellular space. We investigate the conditions allowing learning of Boolean rules in a neural network. Even fully excitatory networks show very good learning performances. Moreover, the investigation of the plastic adaptation features optimizing the performance suggests that learning is very sensitive to the extent of the plastic adaptation and the spatial range of synaptic connections.

[55]  arXiv:1709.06978 (cross-list from physics.optics) [pdf, other]
Title: Anisotropic thermal magnetoresistance for an active control of radiative heat transfer
Subjects: Optics (physics.optics); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)

We predict a huge anisotropic thermal magnetoresistance (ATMR) in the near-field radiative heat transfer between magneto-optical particles when the direction of an external magnetic field is changed with respect to the heat current direction. We illustrate this effect with the case of two InSb spherical particles where we find that the ATMR amplitude can reach values of up to 800% for a magnetic field of 5 T, which is many orders of magnitude larger than its spintronic analogue in electronic devices. This thermomagnetic effect could find broad applications in the fields of ultrafast thermal management as well as magnetic and thermal remote sensing.

### Replacements for Thu, 21 Sep 17

[56]  arXiv:1509.04740 (replaced) [pdf, other]
Title: Modeling sequences and temporal networks with dynamic community structures
Comments: 15 Pages, 6 figures, 2 tables
Journal-ref: Nature Communications 8, 582 (2017)
Subjects: Social and Information Networks (cs.SI); Statistical Mechanics (cond-mat.stat-mech); Physics and Society (physics.soc-ph); Machine Learning (stat.ML)
[57]  arXiv:1510.02214 (replaced) [pdf, other]
Title: Non-linear conductance in mesoscopic weakly disordered wires -- Interaction and magnetic field asymmetry
Comments: RevTeX, 37 pages, 37 pdf figures ; v2: Sections II, VII, VIII & IX reorganised, refs added
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Disordered Systems and Neural Networks (cond-mat.dis-nn)
[58]  arXiv:1603.00769 (replaced) [pdf, ps, other]
Title: Quantum critical transport at a continuous metal-insulator transition
Journal-ref: Phys. Rev. B 94, 081115(R) (2016)
Subjects: Strongly Correlated Electrons (cond-mat.str-el)
[59]  arXiv:1603.08022 (replaced) [pdf, other]
Title: Orthogonal Magnetization and Symmetry Breaking in Pyrochlore Iridate Eu2Ir2O7
Journal-ref: Nature Physics 13, 599-603 (2017)
Subjects: Strongly Correlated Electrons (cond-mat.str-el)
[60]  arXiv:1608.06450 (replaced) [pdf, other]
Title: Kondo cloud of single heavy quark in cold and dense matter
Authors: Shigehiro Yasui
Subjects: High Energy Physics - Phenomenology (hep-ph); Strongly Correlated Electrons (cond-mat.str-el)
[61]  arXiv:1609.02413 (replaced) [pdf, ps, other]
Title: Macroscopic evolution of mechanical and thermal energy in a harmonic chain with random flip of velocities
Subjects: Probability (math.PR); Statistical Mechanics (cond-mat.stat-mech); Mathematical Physics (math-ph)
[62]  arXiv:1609.07123 (replaced) [pdf, other]
Title: Fractional quantum Hall states of bosons on cones
Journal-ref: Phys. Rev. A 96, 033622 (2017)
Subjects: Quantum Gases (cond-mat.quant-gas); Strongly Correlated Electrons (cond-mat.str-el); Optics (physics.optics)
[63]  arXiv:1609.08040 (replaced) [pdf, other]
Title: Dimension reduction for the micromagnetic energy functional on curved thin films
Subjects: Analysis of PDEs (math.AP); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Materials Science (cond-mat.mtrl-sci); Mathematical Physics (math-ph)
[64]  arXiv:1610.02244 (replaced) [pdf, other]
Title: The Tensor Network Theory
Comments: Updated to published version. 20 pages + 15 pages of appendices
Journal-ref: J. Stat. Mech. 093102 (2017)
Subjects: Quantum Physics (quant-ph); Other Condensed Matter (cond-mat.other)
[65]  arXiv:1610.02459 (replaced) [pdf, other]
Title: Anomalous Nernst Effect in Dirac Semimetal Cd3As2
Journal-ref: Phys. Rev. Lett. 118, 136601 (2017)
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Other Condensed Matter (cond-mat.other)
[66]  arXiv:1610.10091 (replaced) [pdf, ps, other]
Title: Transient terahertz photoconductivity of insulating cuprates
Journal-ref: Phys. Rev. B 96, 115133 (2017)
Subjects: Strongly Correlated Electrons (cond-mat.str-el)
[67]  arXiv:1611.01039 (replaced) [pdf, other]
Title: Entanglement spectra of superconductivity ground states on the honeycomb lattice
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Quantum Physics (quant-ph)
[68]  arXiv:1612.06972 (replaced) [pdf, other]
Title: Anomalous Hall Effect in ZrTe5
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
[69]  arXiv:1701.07750 (replaced) [pdf, other]
Title: Skyrmion Gas Manipulation for Probabilistic Computing
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Disordered Systems and Neural Networks (cond-mat.dis-nn); Computational Physics (physics.comp-ph)
[70]  arXiv:1702.08446 (replaced) [pdf, ps, other]
Title: Monte Carlo on manifolds: sampling densities and integrating functions
Comments: New version. 32 pages, 11 figures
Subjects: Numerical Analysis (math.NA); Statistical Mechanics (cond-mat.stat-mech); Computation (stat.CO)
[71]  arXiv:1703.09736 (replaced) [pdf, other]
Title: Graphene-based Josephson junction single photon detector
Comments: 11 pages, 6 figures, and 1 table in the main text
Journal-ref: Phys. Rev. Applied 8, 024022 (2017)
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Materials Science (cond-mat.mtrl-sci); Superconductivity (cond-mat.supr-con)
[72]  arXiv:1704.03015 (replaced) [pdf, other]
Title: Tensor network simulation of QED on infinite lattices: learning from (1+1)d, and prospects for (2+1)d
Authors: Kai Zapp, Roman Orus
Comments: 14 pages, 12 figures, 2 tables. Final version
Journal-ref: Phys. Rev. D 95, 114508 (2017)
Subjects: High Energy Physics - Lattice (hep-lat); Strongly Correlated Electrons (cond-mat.str-el); Quantum Physics (quant-ph)
[73]  arXiv:1704.08602 (replaced) [pdf, other]
Title: Optical conductivity in multiferroic GaV$_4$S$_8$ and GeV$_4$S$_8$: Phonons and electronic transitions
Subjects: Strongly Correlated Electrons (cond-mat.str-el)
[74]  arXiv:1704.08800 (replaced) [pdf, other]
Title: Dirac Cone in two dimensional bilayer graphene by intercalation with V, Nb, and Ta transition metals
Comments: 36 Pages, 9 Figures. arXiv admin note: text overlap with arXiv:1610.04777
Subjects: Materials Science (cond-mat.mtrl-sci)
[75]  arXiv:1705.05119 (replaced) [pdf, other]
Title: Instability of Dirac semimetal phase under strong magnetic field
Subjects: Materials Science (cond-mat.mtrl-sci)
[76]  arXiv:1705.05372 (replaced) [pdf, other]
Title: Construction of Hamiltonians by machine learning of energy and entanglement spectra
Subjects: Strongly Correlated Electrons (cond-mat.str-el); Statistical Mechanics (cond-mat.stat-mech); Computational Physics (physics.comp-ph)
[77]  arXiv:1705.06724 (replaced) [pdf, ps, other]
Title: Self-Learning Monte Carlo Method: Continuous-Time Algorithm
Comments: 6 pages, 5 figures + 2 page supplemental materials, to be published in Phys. Rev. B Rapid communication section
Subjects: Strongly Correlated Electrons (cond-mat.str-el); Disordered Systems and Neural Networks (cond-mat.dis-nn)
[78]  arXiv:1705.08117 (replaced) [pdf, ps, other]
Title: Superposition of Macroscopically Distinct States in Adiabatic Quantum Computation
Authors: Tatsuro Yuge
Subjects: Quantum Physics (quant-ph); Statistical Mechanics (cond-mat.stat-mech)
[79]  arXiv:1706.01179 (replaced) [pdf, other]
Title: Anomalous Thermodynamic Properties of Electron Accumulation Layer in SrTiO$_{3}$
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
[80]  arXiv:1706.02127 (replaced) [pdf, other]
Title: The importance of the weak: Interaction modifiers in artificial spin ices
Authors: Erik Östman (1), Henry Stopfel (1), Ioan-Augustin Chioar (1), Unnar B. Arnalds (2), Aaron Stein (3), Vassilios Kapaklis (1), Björgvin Hjörvarsson (1) ((1) Department of Physics and Astronomy, Uppsala University (2) Science Institute, University of Iceland (3) Center for Functional Nanomaterials, Brookhaven National Laboratory)
Comments: 17 pages, including methods, 4 figures. Supplementary information contains 16 pages and 15 figures
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Other Condensed Matter (cond-mat.other)
[81]  arXiv:1706.06793 (replaced) [pdf, ps, other]
Title: Continuous-time random-walk model for anomalous diffusion in expanding media
Comments: 36 pages, 4 figures (v2: corrected typos, improved notation, three new references and a new appendix)
Journal-ref: Physical Review E 96, 032117 (2017)
Subjects: Statistical Mechanics (cond-mat.stat-mech)
[82]  arXiv:1706.09841 (replaced) [pdf, ps, other]
Title: Heitler-London model for acceptor-acceptor interactions in doped semiconductors
Subjects: Materials Science (cond-mat.mtrl-sci); Disordered Systems and Neural Networks (cond-mat.dis-nn)
[83]  arXiv:1706.09941 (replaced) [pdf, other]
Title: Quantum transfer-matrices for the sausage model
Subjects: High Energy Physics - Theory (hep-th); Statistical Mechanics (cond-mat.stat-mech); Mathematical Physics (math-ph)
[84]  arXiv:1706.10227 (replaced) [pdf, other]
Title: Levitated optomechanics with a fiber Fabry-Perot interferometer
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Optics (physics.optics); Quantum Physics (quant-ph)
[85]  arXiv:1707.02984 (replaced) [pdf, other]
Title: Transport properties across the many-body localization transition in quasiperiodic and random systems
Comments: 15 pages, 15 figures. Published version
Journal-ref: Phys. Rev. B 96, 104205 (2017)
Subjects: Disordered Systems and Neural Networks (cond-mat.dis-nn); Statistical Mechanics (cond-mat.stat-mech); Strongly Correlated Electrons (cond-mat.str-el)
[86]  arXiv:1708.05527 (replaced) [pdf, other]
Title: Real-space investigation of short-range magnetic correlations in fluoride pyrochlores NaCaCo$_2$F$_7$ and NaSrCo$_2$F$_7$ with magnetic pair distribution function analysis
Subjects: Strongly Correlated Electrons (cond-mat.str-el); Materials Science (cond-mat.mtrl-sci)
[87]  arXiv:1709.00109 (replaced) [pdf, ps, other]
Title: Anomalous Thermoelectric Response in an Orbital-Ordered Oxide Near and Far from Equilibrium
Comments: 5 pages, 3 figures, Selected as Editors' Choice
Journal-ref: J. Phys. Soc. Jpn. 86, 093707 (2017)
Subjects: Strongly Correlated Electrons (cond-mat.str-el); Materials Science (cond-mat.mtrl-sci)
[88]  arXiv:1709.03838 (replaced) [pdf, other]
Title: Free-standing magnetic nano-membranes for electron spin-filtering applications
Comments: 5 pages, 3 figures + 6 pages, 6 figures supplementary information
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
[89]  arXiv:1709.04505 (replaced) [pdf]
Title: Highly Sensitive, Large-Area MoS2 Photodetectors with Graphene Contacts
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
[90]  arXiv:1709.04620 (replaced) [pdf, ps, other]
Title: Random matrix approach for primal-dual portfolio optimization problems
Subjects: Portfolio Management (q-fin.PM); Disordered Systems and Neural Networks (cond-mat.dis-nn); Computational Engineering, Finance, and Science (cs.CE); Learning (cs.LG); Optimization and Control (math.OC)
[91]  arXiv:1709.04844 (replaced) [pdf]
Title: Magnetic field suppression of Andreev conductance at superconductor-graphene interfaces
Journal-ref: 2D Mater. 4 (2017) 045011
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Superconductivity (cond-mat.supr-con)
[92]  arXiv:1709.05270 (replaced) [pdf, ps, other]
Title: Triviality of the ground-state metastate in long-range Ising spin glasses in one dimension
Comments: 18 pages. v2: subsection on bond-diluted models added, few extra references. 19 pages
Subjects: Statistical Mechanics (cond-mat.stat-mech); Disordered Systems and Neural Networks (cond-mat.dis-nn); Mathematical Physics (math-ph)
[93]  arXiv:1709.06150 (replaced) [pdf, other]
Title: Tunable Anomalous Andreev Reflection and Triplet Pairings in Spin Orbit Coupled Graphene
Journal-ref: Phys. Rev. B 94, 125415 (2016)
Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Strongly Correlated Electrons (cond-mat.str-el); Superconductivity (cond-mat.supr-con)
[94]  arXiv:1709.06259 (replaced) [pdf, other]
Title: Quantum Entanglement of the Sachdev-Ye-Kitaev Models
Comments: 9 pages, 5 figures; fixed typo in the title
Subjects: Strongly Correlated Electrons (cond-mat.str-el); Statistical Mechanics (cond-mat.stat-mech); High Energy Physics - Theory (hep-th)
[95]  arXiv:1709.06482 (replaced) [pdf, other]
Title: Evolution of inverse cascades and formation of precondensate in Gross-Pitaevskii turbulence in two dimensions