The magnonic functionalities of magnonic devices, such as logic gates, majority gates, and multiplexers, critically depend on anisotropic spin-wave dispersions. Further, each magnonic function utilizes the advantages of distinct spin-wave modes. However, thus far, no method of directly combining magnonic functions to construct an integrated magnonic circuit has been proposed. Therefore, this paper presents a method for the interconversion of surface spin-waves and backward volume spin-waves using a thermoelectrically controlled magnetization gradient. The results of time- and frequency-domain spectroscopies, heat transfer analyses, and micromagnetic simulations demonstrate the effectiveness of the proposed method, through which spin-wave interconversion via thermoelectric control may be employed to develop integrated magnonic circuits.

We analyze biased ensembles of trajectories for a two-dimensional system of particles, evolving by Langevin dynamics in a channel geometry. This bias controls the degree of particle clustering. On biasing to large clustering, we observe a dynamical phase transition where the particles break symmetry and accumulate at one of the walls. We analyze the mechanical properties of this symmetry-broken state using the Irving-Kirkwood stress tensor. The biased ensemble is characterized by body forces that originate in random thermal noises, but they have finite averages in the presence of the bias. We discuss the connection of these forces to Doob's transform and optimal control theory.

Weyl fermions (WFs) in the type-II Weyl semimetal (WSM) ${\mathrm{WTe}}_2$ are difficult to resolve experimentally because the Weyl bands disperse in an extremely narrow region of the ($E\text{−}k$) space. Here, by using DFT-assisted high-resolution ${}^{125}\mathrm{Te}$ solid-state nuclear magnetic resonance (ssNMR) in the temperature range 50–700 K, we succeeded in detecting low energy WF excitations and monitoring their evolution with temperature. Remarkably, WFs are observed to emerge at $T\sim 120$ K, while at lower temperatures ${\mathrm{WTe}}_2$ behaves as a trivial metal. This intriguing phenomenon is induced by the rapid raise of the Fermi level upon heating, which crosses the Weyl bands only for $T>120$ K. The abrupt change of the NMR parameters at this temperature is signature of a topological Lifshitz transition instead of a cursive energy-bands crossing.

Breathing oscillations of skyrmions in chiral antiferromagnets can be excited by a brief modification of the Dzyaloshinskii-Moriya interaction or magnetocrystalline anisotropy strength. We employ an adiabatic approximation and derive a formula for the potential energy that directly implies breathing oscillations. We study the nonlinear regime and the features of larger-amplitude oscillations, and we verify the validity of the adiabatic approximation. We show that there is a maximum amplitude supported by the potential. As a consequence, we predict theoretically and observe numerically skyrmion collapse and subsequent annihilation events due to excitation of large-amplitude breathing oscillations. The process is efficient when the skyrmion is mildly excited so that its radius initially grows, while the annihilation event is eventually induced by the internal breathing dynamics. We reveal the counterintuitive property that the skyrmion possesses a nonzero kinetic energy at the instance of its annihilation. Finally, the frequency of small-amplitude breathing oscillations is determined.

We develop a method for bosonizing the Fermi surface based on the formalism of the coadjoint orbits. This allows one to parametrize the Fermi surface by a bosonic field that depends on the spacetime coordinates and on the position on the Fermi surface. The Wess-Zumino-Witten term in the effective action, governing the adiabatic phase acquired when the Fermi surface changes its shape, is completely fixed. As an effective field theory the action also involves a Hamiltonian, which contains, beside the kinetic energy and the Landau interaction, terms with arbitrary number of derivatives and fields. We show that the resulting local effective field theory captures both linear and nonlinear effects in Landau's Fermi liquid theory. The approach can be extended to incorporate spin degrees of freedom and the charge-2 fields corresponding to the BCS order parameter.

The equilibrium properties of a weakly interacting atomic Bose gas across the Berezinskii-Kosterlitz-Thouless (BKT) and Bose-Einstein condensation (BEC) phase transitions are numerically investigated through a dimensionality crossover from two to three dimensions. The crossover is realized by confining the gas in an experimentally feasible hybridized trap which provides homogeneity along the planar $xy$ directions through a box potential in tandem with a harmonic transverse potential along the transverse $z$ direction. The dimensionality is modified by varying the frequency of the harmonic trap from tight to loose transverse trapping. Our findings, based on a stochastic (projected) Gross-Pitaevskii equation, showcase a continuous shift in the character of the phase transition from BKT to BEC, and a monotonic increase of the identified critical temperature as a function of dimensionality, with the strongest variation exhibited for small chemical potential values up to approximately twice the transverse confining potential.

In graph analyses, directed edges are often approximated to undirected ones so that the adjacency matrices may be symmetric. However, such a simplification has not been thoroughly verified. In this study, we investigate how directedness affects the graph spectra by introducing random directization, which is an opposite operation of neglecting edge directions. We analytically reveal that uniformly random directization typically conserves the relative spectral structure of the adjacency matrix in the perturbative regime. The result of random directization implies that the spectrum of the adjacency matrix can be conserved after the directedness is ignored.

Animals typically forage in groups. Social foraging can help animals avoid predation and decrease their uncertainty about the richness of food resources. Despite this, theoretical mechanistic models of patch foraging have overwhelmingly focused on the behavior of single foragers. In this study, we develop a mechanistic model that accounts for the behavior of individuals foraging together and departing food patches following an evidence accumulation process. Each individual's belief about patch quality is represented by a stochastically accumulating variable, which is coupled to another's belief to represent the transfer of information. We consider a cohesive group, and model information sharing by considering both intermittent pulsatile coupling (only communicate decision to leave) and continuous diffusive coupling (communicate throughout the deliberation process). Groups employing pulsatile coupling can obtain higher foraging efficiency, which depends more strongly on the coupling parameter compared to those using diffusive coupling. Conversely, groups using diffusive coupling are more robust to changes and heterogeneities in belief weighting and departure criteria. Efficiency is measured by a reward rate function that balances the amount of energy accumulated against the time spent in a patch, computed by solving an ordered first passage time problem for the patch departures of each individual. Using synthetic departure time data, we can distinguish between the two modes of communication and identify the model parameters. Our model establishes a social patch foraging framework to identify deliberative decision strategies and forms of social communication, and to allow model fitting to field data from foraging animal groups.

We propose a statistical model of a large random network with high connectivity in order to describe the behavior of E. coli cells after exposure to acute stress. The building blocks of this network are feedback cycles typical of the genetic and metabolic networks of a cell. Each node on the cycles is a spin degree of freedom representing a component in the cell's network that can be in one of two states: active or inactive. The cycles are interconnected by regulation or by the exchange of metabolites. Stress is realized by an external magnetic field that drives the nodes into an inactive state, and the time the magnetization passes zero value for the first time represents the first division event of the cell after the stress period. The numerical and analytical solutions for this first passage problem reproduce the aging dynamics observed in the experimental data.

Quantum key distribution (QKD) enables secure information exchange with untrusted quantum links between remote communication parties. A central task in the studies of QKD protocols is security analysis, which aims at deriving the length of the final key such that it is secure regardless of the eavesdropper's computational power. In literature, the security analysis has been done both analytically and numerically. Compared to analytical methods which tend to require techniques specific to each QKD protocol, numerical ones are more general since they can be directly applied to many QKD protocols with little adaptation. However, current numerical methods are carried out based on some assumptions such as working in the asymptotic limit and collective attacks from eavesdroppers. In this work, we remove these assumptions and develop a numerical finite-size security analysis against general attacks for a large class of QKD protocols. We also give an example of applying the method to the recent phase-matching QKD protocol with a simplified protocol design. Our result shows that the finite-size key rate can surpass the linear key-rate bound with a practical QKD system operated for only several hours.

The growth of axons is a key process in neural system development, which relies upon a subtle balance between external mechanical forces and remodeling of cellular constituents. A key problem in the biophysics of axons is therefore to understand the overall response of the axon under stretch, which is often modeled phenomenologically using morphoelastic or viscoelastic models. Here, we develop a microscopic mixture model of growth and remodeling based on protein turnover and damage to obtain the macroscopic rheology of axonal shafts. First, we provide an estimate for the instantaneous elastic response of axons. Second, we predict that under moderate traction velocities, the axonal core behaves like a viscoelastic Maxwell material whose rheological parameters can be expressed in terms of the microscopic properties. Third, for larger velocities, we show that failure takes place due to extensive damage.

A moving dielectric medium can displace the optical path of light passing through it, a phenomenon known as the Fresnel-Fizeau optical drag effect. The resulting displacement is proportional to the medium's velocity. In this paper, we report on the observation of an anomalous optical drag effect, where the displacement is still proportional to the medium's speed but along the direction opposite to the medium's movement. We conduct an optical drag experiment under conditions of electromagnetically induced transparency and observe the transition from normal, to null, to anomalous optical drag by modification of the two-photon detuning.

For materials where spin-orbit coupling is competitive with electronic correlations, the spatially anisotropic spin-orbital wave functions can stabilize degenerate states that lead to many and diverse quantum phases of matter. Here we find evidence for a dynamical spin-orbital state preceding a $T^{*}$ = 50 K order-disorder spin-orbital ordering transition in the $j=3/2$ lacunar spinel ${\mathrm{GaTa}}_4{\mathrm{Se}}_8$. Above $T^{*}, {\mathrm{GaTa}}_4{\mathrm{Se}}_8$ has an average cubic crystal structure, but total scattering measurements indicate local noncubic distortions of ${\mathrm{Ta}}_4$ tetrahedral clusters for all measured temperatures $2<T<300$ K. Inelastic neutron-scattering measurements reveal the dynamic nature of these local distortions through symmetry forbidden optical phonon modes that modulate $j=3/2$ molecular orbital occupation as well as intercluster Ta-Se bonds. Spin-orbital ordering at $T^{*}$ cannot be attributed to a classic Jahn-Teller mechanism and, based on our findings, we propose that intercluster interactions acting on the scale of $T^{*}$ act to break global symmetry. The resulting staggered intercluster dimerization pattern doubles the unit cell, reflecting a spin-orbital valence bond ground state.