Showing papers in "EPL in 2016"
TL;DR: Complex network analysis of time series opens up new venues to address interdisciplinary challenges in climate dynamics, multiphase flow, brain functions, ECG dynamics, economics and traffic systems.
Abstract: Revealing complicated behaviors from time series constitutes a fundamental problem of continuing interest and it has attracted a great deal of attention from a wide variety of fields on account of its significant importance. The past decade has witnessed a rapid development of complex network studies, which allow to characterize many types of systems in nature and technology that contain a large number of components interacting with each other in a complicated manner. Recently, the complex network theory has been incorporated into the analysis of time series and fruitful achievements have been obtained. Complex network analysis of time series opens up new venues to address interdisciplinary challenges in climate dynamics, multiphase flow, brain functions, ECG dynamics, economics and traffic systems.
242 citations
TL;DR: In this article, the electronic structure and magnetism of CrI3 monolayer, whose bulk material is an interesting layered ferromagnetic (FM) semiconductor, have been investigated using first-principles calculations and a Monte Carlo simulation.
Abstract: Two-dimensional materials are of current great interest for their promising applications to postsilicon microelectronics. Here we study, using first-principles calculations and a Monte Carlo simulation, the electronic structure and magnetism of CrI3 monolayer, whose bulk material is an interesting layered ferromagnetic (FM) semiconductor. Our results show that CrI3 monolayer remains FM with , and the FM order is due to a superexchange in the near-90° Cr-I-Cr bonds. Moreover, we find that an itinerant magnetism could be introduced by carriers doping. Both electron doping and hole doping would render CrI3 monolayer half-metallic, and steadily enhance the FM stability. In particular, hole doping is three times as fast as electron doping in increasing T C, and a room temperature FM half-metallicity could be achieved in CrI3 monolayer via a half-hole doping. Therefore, CrI3 monolayer would be an appealing two-dimensional spintronic material.
143 citations
TL;DR: In this paper, it was shown that conjugate extensive and intensive observables can be defined even in non-equilibrium steady states lacking a free energy, despite the observed stable phase separation.
Abstract: The theoretical understanding of active matter, which is driven out of equilibrium by directed motion, is still fragmental and model oriented. Stochastic thermodynamics, on the other hand, is a comprehensive theoretical framework for driven systems that allows to define fluctuating work and heat. We apply these definitions to active matter, assuming that dissipation can be modelled by effective non-conservative forces. We show that, through the work, conjugate extensive and intensive observables can be defined even in non-equilibrium steady states lacking a free energy. As an illustration, we derive the expressions for the pressure and interfacial tension of active Brownian particles. The latter becomes negative despite the observed stable phase separation. We discuss this apparent contradiction, highlighting the role of fluctuations, and we offer a tentative explanation.
133 citations
TL;DR: In this paper, the lattice contribution to the thermal conductivity of MoS2 strongly dominates the carrier contribution in a broad temperature range from 300 to 800 K, and the length scale for transition between diffusive and ballistic transport is determined.
Abstract: We show that the lattice contribution to the thermal conductivity of MoS2 strongly dominates the carrier contribution in a broad temperature range from 300 to 800 K. Since theoretical insight into the lattice contribution is largely missing, though it would be essential for materials design, we solve the Boltzmann transport equation for the phonons self-consistently in order to evaluate the phonon lifetimes. In addition, the length scale for transition between diffusive and ballistic transport is determined. The low out-of-plane thermal conductivity of bulk MoS2 ( at 300 K) is useful for thermoelectric applications. On the other hand, the thermal conductivity of monolayer MoS2 ( at 300 K) is comparable to that of Si.
122 citations
TL;DR: In this paper, a new quantum master equation which improves shortcomings of the local approach known in the so-called local approach is derived, which does not violate the second law of thermodynamics.
Abstract: A system of sites weakly coupled to each other and to one or more reservoirs (open quantum network) is considered. A new quantum master equation which improves shortcomings of the master equation known in the so-called local approach is derived. The usual quantum master equation describing the weak coupling of the system with reservoir requires the knowledge of eigenvalues and eigenvectors of the Hamiltonian of the system, so it often becomes impractical. By this reason, when the inter-site couplings are weak, the local approach, which neglects the influence of the inter-site couplings on the system-reservoir couplings, is often used. However, recently, it was reported that the local approach master equation leads to the violation of the second law of thermodynamics. We develop a systematic perturbation expansion to derive corrections to the local approach master equation. Using this improvement of the local approach, we derive an expression for the heat flux for a particular model and show that it does not violate the second law of thermodynamics.
115 citations
TL;DR: In this article, the authors consider the non-equilibrium physics induced by joining two tight-binding fermionic chains to form a single chain, where fillings (densities) in the two chains might be different.
Abstract: We consider the non-equilibrium physics induced by joining together two tight-binding fermionic chains to form a single chain. Before being joined, each chain is in a many-fermion ground state. The fillings (densities) in the two chains might be different. We present a number of exact results, focusing on two-point correlators and the Loschmidt echo (return probability). For the non-interacting case, we identify through an exact derivation the regime in which a semiclassical ansatz is valid. We present a number of analytical results beyond semiclassics, such as the approach to the non-equilibrium steady state and the appearance of Tracy-Widom distributions at the front of the light cone. The light cone behavior is quantified through a series expansion in time, and this description is shown to be valid for interacting systems as well. Results on the Loschmidt echo, presented for finite and zero interactions, illustrate that the physics is different from both local and global quenches.
112 citations
TL;DR: In this article, the authors derive the first and second law for resetting processes far from equilibrium and derive a bound on the amount of work required to maintain a resetting process.
Abstract: Stochastic dynamics with random resetting leads to a non-equilibrium steady state. Here, we consider the thermodynamics of resetting by deriving the first and second law for resetting processes far from equilibrium. We identify the contributions to the entropy production of the system which arise due to resetting and show that they correspond to the rate with which information is either erased or created. Using Landauer's principle, we derive a bound on the amount of work that is required to maintain a resetting process. We discuss different regimes of resetting, including a Maxwell demon scenario where heat is extracted from a bath at constant temperature.
100 citations
TL;DR: In this article, the anomalous Hall conductivity in some ferromagnetic and antiferromagnetic Heusler compounds was theoretically and experimentally found to be exceptionally large, and the appearance of Weyl points near the Fermi energy was investigated.
Abstract: The anomalous Hall conductivity (AHC) in some ferromagnetic and antiferromagnetic Heusler compounds was theoretically and experimentally found to be exceptionally large. For the case of ferromagnetic Co2MnAl we here argue that the large AHC is connected with the appearance of Weyl points near the Fermi energy. We find four Weyl points slightly above the Fermi edge. We describe our analysis for a magnetization being in the (110)-direction. For the possible (100)-direction we find at least four Weyl points, too. We predict that Co2MnGa also possesses Weyl points near or at the Fermi energy.
100 citations
TL;DR: In this paper, the autaptic transmission delay is identified as a key parameter that controls the firing patterns and determines multistability regions of fast-spiking interneurons.
Abstract: Fast-spiking (FS) interneurons in the brain are self-innervated by powerful inhibitory GABAergic autaptic connections. By computational modelling, we investigate how autaptic inhibition regulates the firing response of such interneurons. Our results indicate that autaptic inhibition both boosts the current threshold for action potential generation and modulates the input-output gain of FS interneurons. The autaptic transmission delay is identified as a key parameter that controls the firing patterns and determines multistability regions of FS interneurons. Furthermore, we observe that neuronal noise influences the firing regulation of FS interneurons by autaptic inhibition and extends their dynamic range for encoding inputs. Importantly, autaptic inhibition modulates noise-induced irregular firing of FS interneurons, such that coherent firing appears at an optimal autaptic inhibition level. Our results reveal the functional roles of autaptic inhibition in taming the firing dynamics of FS interneurons.
87 citations
TL;DR: In this article, the authors studied the atypically large deviations of the height at the origin at late times in the Kardar-Parisi-Zhang (KPZ) universality class.
Abstract: We study the atypically large deviations of the height $H \sim {{\cal O}}(t)$ at the origin at late times in $1+1$-dimensional growth models belonging to the Kardar-Parisi-Zhang (KPZ) universality class. We present exact results for the rate functions for the discrete single step growth model, as well as for the continuum KPZ equation in a droplet geometry. Based on our exact calculation of the rate functions we argue that models in the KPZ class undergo a third order phase transition from a strong coupling to a weak coupling phase, at late times.
86 citations
TL;DR: In this paper, the authors carried out measurements of domain wall velocities driven by magnetic-field pulses in symmetric Pt/Co/Pt and asymmetric asymmetric P Pt, Co/Gd and Co/AlOx trilayers with ultrathin Co layers and perpendicular magnetic anisotropy.
Abstract: We carried out measurements of domain wall (DW) velocities driven by magnetic-field pulses in symmetric Pt/Co/Pt and asymmetric Pt/Co/AlOx, Pt/Co/GdOx and Pt/Co/Gd trilayers with ultrathin Co layers and perpendicular magnetic anisotropy. The maximum observed velocity is much larger in the asymmetric samples, where the interfacial Dzyaloshinskii-Moriya interaction (DMI) stabilises chiral Neel walls. In quantitative agreement with analytical models, in all samples the maximum observed DW speed scales as , where D is the strength of the DMI and the spontaneous magnetisation. In Pt/Co/Gd, where the anti-parallel coupling between the magnetic moments of Gd and Co leads to a decrease of the total magnetisation, very large DW speeds (up to 700 m/s) are obtained.
TL;DR: In this paper, the statistics of the local resolvent and non-ergodic properties of eigenvectors for a generalised Rosenzweig-Porter random matrix model were studied.
Abstract: We study the statistics of the local resolvent and non-ergodic properties of eigenvectors for a generalised Rosenzweig-Porter random matrix model, undergoing two transitions separated by a delocalised non-ergodic phase. Interpreting the model as the combination of on-site random energies and a structurally disordered hopping, we found that each eigenstate is delocalised over sites close in energy in agreement with Kravtsov et al. (New J. Phys., 17 (2015) 122002). Our other main result, obtained combining a recurrence relation for the resolvent matrix with insights from Dyson's Brownian motion, is to show that the properties of the non-ergodic delocalised phase can be probed studying the statistics of the local resolvent in a non-standard scaling limit.
TL;DR: In this article, the authors considered a quantum Otto refrigerator cycle of a time-dependent harmonic oscillator and derived analytical expressions for the optimal performance both in the high-temperature (classical) regime and in the low-temporal limit.
Abstract: We consider a quantum Otto refrigerator cycle of a time-dependent harmonic oscillator. We investigate the coefficient of performance at maximum figure of merit for adiabatic and nonadiabatic frequency modulations. We obtain analytical expressions for the optimal performance both in the high-temperature (classical) regime and in the low-temperature (quantum) limit. We moreover analyze the breakdown of the cooling cycle for strongly nonadiabatic driving protocols and derive analytical estimates for the minimal driving time allowed for cooling.
TL;DR: In this paper, the authors review developments in this field related to the study of incoherent nonequilibrium electron dynamics, the analysis of interactions between electrons and collective excitations, the exploration of dressed-state physics, and the illumination of unoccupied band structure.
Abstract: Techniques in time- and angle-resolved photoemission spectroscopy have facilitated a number of recent advances in the study of quantum materials. We review developments in this field related to the study of incoherent nonequilibrium electron dynamics, the analysis of interactions between electrons and collective excitations, the exploration of dressed-state physics, and the illumination of unoccupied band structure. Future prospects are also discussed.
TL;DR: In this paper, the impact of the interaction of nodes in a layer of a multiplex network on the dynamical behavior and cluster synchronization of these nodes in the other layers is studied.
Abstract: We study the impact of the interaction of nodes in a layer of a multiplex network on the dynamical behavior and cluster synchronization of these nodes in the other layers. We find that nodes interactions in one layer affect the cluster synchronizability of the other layer in many different ways. While the multiplexing of a sparse network with the other sparse networks enhances the cluster synchronizability of the individual layer, multiplexing with dense networks suppresses the cluster synchronizability with the network architecture deciding the impact of the enhancement and the suppression. Additionally, at weak couplings the enhancement in the cluster synchronizability, due to multiplexing, remains of the driven type, while for strong couplings the multiplexing may lead to a transition to the self-organized mechanism. The results presented here have applicability in regulating the synchronizability of a particular layer of real-world systems having multiplex architecture.
TL;DR: In this paper, the large deviation functions characterizing the long-time fluctuations of the occupation of drifted Brownian motion were calculated and shown to have non-analytic points, which is the first example of dynamical phase transition that appears in a simple, homogeneous Markov process without an additional low-noise, large-volume or hydrodynamic scaling limit.
Abstract: We calculate the large deviation functions characterizing the long-time fluctuations of the occupation of drifted Brownian motion and show that these functions have non-analytic points. This provides the first example of dynamical phase transition that appears in a simple, homogeneous Markov process without an additional low-noise, large-volume or hydrodynamic scaling limit.
TL;DR: In this paper, the authors provide a synthesis between different viewpoints on soft wetting (microscopic and macroscopic, mechanics and thermodynamics), and point out key open issues in the field.
Abstract: Extremely compliant elastic materials, such as thin membranes or soft gels, can be deformed when wetted by a liquid drop. It is commonly assumed that the solid capillarity in "soft wetting" can be treated in the same manner as liquid surface tension. However, the physical chemistry of a solid interface is itself affected by any distortion with respect to the elastic reference state. This gives rise to phenomena that have no counterpart in liquids: the mechanical surface stress is different from the excess free energy in surface. Here we point out some striking consequences of this "Shuttleworth effect" in the context of wetting on deformable substrates, such as the appearance of elastic singularities and unconventional capillary forces. We provide a synthesis between different viewpoints on soft wetting (microscopic and macroscopic, mechanics and thermodynamics), and point out key open issues in the field.
TL;DR: In this article, it was shown that both the conductivity and resistivity tensors exhibit robust anomalies in a magnetic field B, while the Hall angle exhibits an unusual profile approaching a step function.
Abstract: Na3Bi is a Dirac semimetal with protected nodes that may be sensitive to the breaking of time-reversal invariance in a magnetic field B. We report experiments which reveal that both the conductivity and resistivity tensors exhibit robust anomalies in B. The resistivity is B-linear up to 35 T, while the Hall angle exhibits an unusual profile approaching a step function. The conductivities and share identical power-law dependences at large B. We propose that these significant deviations from conventional transport result from an unusual sensitivity of the transport lifetime to B. The transport features are compared with those in Cd3As2.
TL;DR: In this article, the authors show that the disjoining pressure at small separations for the charge regulation boundary condition depends on the details of the dissociation/association process and that the limit of charge regulation is a separate boundary condition.
Abstract: The three most commonly used boundary conditions for charged colloidal systems are constant charge (insulator), constant potential (conducting electrode) and charge regulation (ionizable groups at the surface). It is usually believed that the charge regulation is a generalized boundary condition that reduces in some specific limits to either constant-charge or constant-potential boundary conditions. By computing the disjoining pressure between two symmetric planes for these three boundary conditions, both numerically (for all inter-plate separations) and analytically (for small inter-plate separations), we show that this is not, in general, the case. In fact, the limit of charge regulation is a separate boundary condition, yielding a disjoining pressure with a different characteristic separation scaling. Our findings are supported by several examples demonstrating that the disjoining pressure at small separations for the charge regulation boundary condition depends on the details of the dissociation/association process.
TL;DR: In this paper, the authors investigate non-locally coupled identical chaotic maps with delayed interactions in the multiplex network framework and find that an interplay of delay and multiplexing brings about an enhanced or suppressed appearance of the chimera state depending on the distribution as well as the parity of delay values in the layers.
Abstract: The chimera state with co-existing coherent and incoherent dynamics has recently attracted a lot of attention due to its wide applicability. We investigate non-locally coupled identical chaotic maps with delayed interactions in the multiplex network framework and find that an interplay of delay and multiplexing brings about an enhanced or suppressed appearance of the chimera state depending on the distribution as well as the parity of delay values in the layers. Additionally, we report a layer chimera state with the existence of one layer exhibiting coherent and another layer incoherent dynamical evolution. The rich variety of dynamical behavior demonstrated here can be used to gain further insight into the real-world networks which inherently possess such multi-layer architecture with delayed interactions.
TL;DR: In this article, the amount of mechanical energy dissipated by out-of-equilibrium living organisms is predicted by using a minimal microscopic model, which includes complex rheological effects and nonequilibrium stochastic forces.
Abstract: Living organisms are inherently out-of-equilibrium systems. We employ recent developments in stochastic energetics and rely on a minimal microscopic model to predict the amount of mechanical energy dissipated by such dynamics. Our model includes complex rheological effects and nonequilibrium stochastic forces. By performing active microrheology and tracking micron-sized vesicles in the cytoplasm of living oocytes, we provide unprecedented measurements of the spectrum of dissipated energy. We show that our model is fully consistent with the experimental data, and we use it to offer predictions for the injection and dissipation energy scales involved in active fluctuations.
TL;DR: In this article, the normal-state Hall coefficient from the resonating-valence-bond spin-liquid model was calculated for high-T c cuprates and it was shown that at low temperatures, a switch from a downturn to an upturn in the Hall coefficient signals the departure of the electron-like pockets from the Fermi surface.
Abstract: The mechanism by which the Fermi surface of high-T c cuprates undergoes a dramatic change from a large hole-like barrel to small arcs or pockets on entering the pseudogap phase remains a question of fundamental importance. Here we calculate the normal-state Hall coefficient from the resonating-valence-bond spin-liquid model developed by Yang, Rice and Zhang. In this model, reconstruction of the Fermi surface occurs via an intermediate regime where the Fermi surface consists of both hole- and electron-like pockets. We find that the doping (x ) dependence of the Hall number transitions from to (x ) over this narrow doping range. At low temperatures, a switch from a downturn to an upturn in the Hall coefficient signals the departure of the electron-like pockets from the Fermi surface.
TL;DR: A supervised classification aiming at discriminating informative from imaginative documents is performed using a networked model that describes the local topological/dynamical properties of function words and achieves an accuracy rate of up to 95%, which is much higher than similar networked approaches.
Abstract: Statistical methods have been widely employed in recent years to grasp many language properties. The application of such techniques have allowed an improvement of several linguistic applications, such as machine translation and document classification. In the latter, many approaches have emphasised the semantical content of texts, as is the case of bag-of-word language models. These approaches have certainly yielded reasonable performance. However, some potential features such as the structural organization of texts have been used only in a few studies. In this context, we probe how features derived from textual structure analysis can be effectively employed in a classification task. More specifically, we performed a supervised classification aiming at discriminating informative from imaginative documents. Using a networked model that describes the local topological/dynamical properties of function words, we achieved an accuracy rate of up to 95%, which is much higher than similar networked approaches. A systematic analysis of feature relevance revealed that symmetry and accessibility measurements are among the most prominent network measurements. Our results suggest that these measurements could be used in related language applications, as they play a complementary role in characterising texts.
TL;DR: In this paper, a generalized (2+1)-dimensional Boussinesq equation is used to describe the propagation of small-amplitude, long wave in shallow water.
Abstract: Under investigation in this work is a generalized (2+1)-dimensional Boussinesq equation, which can be used to describe the propagation of small-amplitude, long wave in shallow water. By virtue of Bell's polynomials, an effective way is presented to succinctly construct its bilinear form. Furthermore, based on the bilinear formalism and the extended homoclinic test method, the breather wave solution, rogue-wave solution and solitary-wave solution of the equation are well constructed. Our results can be used to enrich the dynamical behavior of the generalized (2+1)-dimensional nonlinear wave fields.
TL;DR: In this paper, a nonlinear oscillator model with negative time-delayed feedback is studied numerically under external deterministic and stochastic forcing, and it is shown that in the unforced system complex partial synchronization patterns like chimera states and salt-and-pepper-like solitary states arise on the route from regular dynamics to spatio-temporal chaos.
Abstract: A nonlinear oscillator model with negative time-delayed feedback is studied numerically under external deterministic and stochastic forcing. It is found that in the unforced system complex partial synchronization patterns like chimera states as well as salt-and-pepper–like solitary states arise on the route from regular dynamics to spatio-temporal chaos. The control of the dynamics by external periodic forcing is demonstrated by numerical simulations. It is shown that one-cluster and multi-cluster chimeras can be achieved by adjusting the external forcing frequency to appropriate resonance conditions. If a stochastic component is superimposed to the deterministic external forcing, chimera states can be induced in a way similar to stochastic resonance, they appear, therefore, in regimes where they do not exist without noise.
TL;DR: In this article, the inverse Rashba-Edelstein effect is measured in the 2D electron liquid existing at the interface between LaAlO3 and SrTiO3, and the effect is found to be larger than in the highly Rashba split Bi/Ag interface which is attributed to an amplifying effect due to a long carrier's momentum lifetime.
Abstract: Spin-to-charge conversion using the inverse Rashba-Edelstein effect is measured in the 2D electron liquid existing at the interface between LaAlO3 and SrTiO3. The effect is found to be larger than in the highly Rashba split Bi/Ag interface which we attribute to an amplifying effect due to a long carrier's momentum lifetime. The explanation is supported by temperature measurements and the Rashba field is also shown to be anisotropic in the interface plane.
TL;DR: In this article, the authors show that there exists an optimal hierarchical depth for the determination of collective influence that they use to describe the potency of players for passing their strategies, which depends on the strength of the social dilemma.
Abstract: When evolutionary games are contested in structured populations, the degree of each player in the network plays an important role. If they exist, hubs often determine the fate of the population in remarkable ways. Recent research based on optimal percolation in random networks has shown, however, that the degree is neither the sole nor the best predictor of influence in complex networks. Low-degree nodes may also be optimal influencers if they are hierarchically linked to hubs. Taking this into account leads to the formalism of collective influence in complex networks, which as we show here, has far-reaching implications for the favorable resolution of social dilemmas. In particular, there exists an optimal hierarchical depth for the determination of collective influence that we use to describe the potency of players for passing their strategies, which depends on the strength of the social dilemma. Interestingly, the degree, which corresponds to the baseline depth zero, is optimal only when the temptation to defect is small. Our research reveals that evolutionary success stories are related to spreading processes which are rooted in favorable hierarchical structures that extend beyond local neighborhoods.
TL;DR: In this paper, the critical radius of local models is defined and a necessary and sufficient condition for a two-qubit state to be steerable with respect to projective measurements.
Abstract: Fully characterizing the steerability of a quantum state of a bipartite system has remained an open problem ever since the concept of steerability was first defined. In this paper, using our recent geometrical approach to steerability, we suggest a necessary and sufficient condition for a two-qubit state to be steerable with respect to projective measurements. To this end, we define the critical radius of local models and show that a state of two qubits is steerable with respect to projective measurements from Alice's side if and only if her critical radius of local models is less than 1. As an example, we calculate the critical radius of local models for the so-called T-states by proving the optimality of a recently suggested local hidden state model.
TL;DR: Farage et al. as mentioned in this paper employed dynamical density functional theory to determine the steady-state density profiles in an effective equilibrium system and predicted wetting and drying transitions at a flat repulsive wall and capillary condensation and evaporation in a slit pore.
Abstract: A simple theoretical approach is used to investigate active colloids at the free interface and near repulsive substrates. We employ dynamical density functional theory to determine the steady-state density profiles in an effective equilibrium system (Farage T. F. F. et al. , Phys. Rev. E , 91 (2015) 042310). In addition to the known accumulation at surfaces, we predict wetting and drying transitions at a flat repulsive wall and capillary condensation and evaporation in a slit pore. These new phenomena are closely related to the motility-induced phase separation (MIPS) in the bulk.
TL;DR: A novel variational argument is provided which overcomes this problem, and correctly predicts the scaling properties of soft modes near the jamming transition, and is verified numerically.
Abstract: Amorphous solids tend to present an abundance of soft elastic modes, which diminish their transport properties, generate heterogeneities in their elastic response, and affect non-linear processes like thermal activation of plasticity. This is especially true in packings of particles near their jamming transition, for which effective medium theory and variational arguments can both predict the density of vibrational modes. However, recent numerics support that one hypothesis of the variational argument does not hold. We provide a novel variational argument which overcomes this problem, and correctly predicts the scaling properties of soft modes near the jamming transition. Soft modes are shown to be related to the response to a local strain in more connected networks, and to be characterized by a volume , where is the excess coordination above the Maxwell threshold. These predictions are verified numerically.