The planar Hall effect is a phenomenon that the Hall conductivity emerges perpendicular to the electric field in the presence of an in-plane magnetic field. We investigate the planar Hall effect in two-dimensional metal coupled with higher symmetric $X$-wave magnets with $X=p,d,f,g,i$, where those with $X=d,g,i$ are altermagnets. The $X$-wave magnet is characterized by the number $N_X$ of the nodes in the band structure, where $N_X=1,2,3,4,6$ corresponds to $X=p,d,f,g,i$. Although the system is metallic, provided the Dirac gap is tiny, we demonstrate that the Hall conductivities are almost half quantized and well approximated by the formula ${\sigma }_{xy}=\pm (e^2/2h)\mathrm{sgn}(Jsin{N}_X\mathrm{\Phi })$, where $J$ is the coefficient of the coupling between the $X$-wave magnet and the electrons and $\mathrm{\Phi }$ is the direction of the applied magnetic field. Hence, the Hall conductivity is periodic in $\mathrm{\Phi }$, and the periodicity is equal to the number $N_X$ of the nodes. This property may be used to confirm that the target material is indeed an $X$-wave magnet. Furthermore, the sign of $J$ may be used as a bit for antiferromagnetic spintronics.

GaN/AlN interfaces are essential in advanced high-power and high-frequency electronic devices, where effective thermal management is crucial for optimal performance and reliability. This work investigates the thermal boundary conductance (TBC) of standalone and nonstandalone GaN/AlN heterostructures using nonequilibrium molecular dynamics (NEMD) driven by accurate machine learning interatomic potentials trained from density-functional theory calculations. For the standalone interface, the TBC is found to be $\sim 600\mathrm{MW}{\mathrm{m}}^{-2}{\mathrm{K}}^{-1}$ at room temperature after quantum correction. The result revises previous NEMD predictions ($400–2000\mathrm{MW}{\mathrm{m}}^{-2}{\mathrm{K}}^{-1}$) using empirical interatomic potentials. When a second GaN/AlN interface is brought close to the original interface, the TBC of the original interface can increase to $1000\mathrm{MW}{\mathrm{m}}^{-2}{\mathrm{K}}^{-1}$, and this value gradually decreases with increasing distance between the two interfaces. When more interfaces are introduced in proximity, the original interface's TBC can be further enhanced to above $1150\mathrm{MW}{\mathrm{m}}^{-2}{\mathrm{K}}^{-1}$. After comparing double interfaces, superlattices, and random multilayers, it is concluded that such enhancement of TBC is not caused by the emergence of superlattice modes but rather by the ballistic transport of the existing phonon modes of each material. Additionally, a “critical separation distance” ($l_{\mathrm{cs}}$) is defined as the threshold beyond which the two interfaces no longer influence each other and behave independently. $l_{\mathrm{cs}}$ is determined by the mean free path of the phonons filtered by the interfaces that transport in the middle layer between two interfaces. Our findings provide insights into the thermal transport mechanisms that may aid the design of future electronic devices.

The harnessing of quantum resources provides unique advantages in both information processing and energy conversion, without any classical analogy. This work presents a theoretical investigation of quantum-enhanced thermoelectric transport in a three-terminal double-quantum-dot system coupled to a squeezed photon reservoir. By developing a comprehensive quantum master equation approach that incorporates full counting statistics, we reveal how squeezed thermal reservoirs fundamentally modify nanoscale energy conversion processes. The analysis demonstrates that quantum coherence and squeezing serve as crucial quantum resources, enabling simultaneous optimization of thermodynamic performance and generation of steady-state entanglement. Furthermore, the work identifies distinct regimes of quantum fluctuation statistics regulated by squeezing parameters. These results advance our understanding of quantum effects in nanoscale energy conversion and open new possibilities for designing coherent thermoelectric devices.

Structural symmetry breaking in two-dimensional systems introduces additional electronic degrees of freedom, fostering exotic quantum phenomena such as the Rashba effect, magnetic anisotropy, and nontrivial topological states, thereby advancing their relevance in spintronic, valleytronic, and quantum information technologies. In the present density functional theory investigation on $\mathrm{Ta}QX$ $(Q=\mathrm{O}, \mathrm{S}; X=\mathrm{F}, \mathrm{Cl}, \mathrm{Br})$ Janus monolayers, possessing intrinsic mirror asymmetry and permanent out-of-plane dipole moments, we aim at boosting Rashba dynamics via application of external electric field and biaxial strain. All six systems are not only phonon-stable across a broad strain window but also thermodynamically durable as per room-temperature ab initio molecular dynamics and exhibit spontaneous formation potential. Phonon dispersion and factor group analysis reveal simultaneously Raman and infrared (IR)-active vibrational modes $(E^{1,2},A_1^{1,2})$, reaffirming the absence of an inversion center. All monolayers are semiconductors with indirect (except TaOF) band gaps, spanning from the near-IR to visible range, promising for optospintronic applications. Foremost, strong spin-orbit coupling facilitates substantial Rashba-type spin splitting near the $\mathrm{\Gamma }$ point at the valence band maximum, with Rashba coefficients ranging between ${\alpha }_R=122\text{and}330\mathrm{meV}\AA$. Application of out-of-plane electric field and in-plane biaxial strain modulates ${\alpha }_R$, maximizing it up to 4.25 times $(\sim 1.4\mathrm{eV}\AA )$ for TaOF. Furthermore, huge strain-induced Rashba anisotropy emerges along the $\mathrm{\Gamma }\text{−}K$ and $\mathrm{\Gamma }\text{−}M$ directions, reaching 58 meV Å in 5% tensed TaOF. Elevated ${\alpha }_R$ coupled with pronounced anisotropy in structurally robust TaOF unlocks crystallographically dictated spin splitting, directional manipulation of spin-momentum locking, nonreciprocal spin transport, and spin filtering, essential for next-generation spintronic integration.

Localization of wave functions in disordered systems can be characterized by the Lyapunov exponent, which is zero in the extended phase and nonzero in the localized phase. Previous studies have shown that this exponent is an analytic function of eigenenergy in a given phase; thus, its nonanalytic behavior has been commonly used to determine the boundaries between the extended and localized phases. In this work, we show that if the localization centers are inhomogeneous across the whole chain and the system possesses (at least) two different localization modes, the Lyapunov exponent can become nonanalytic in the localized phase at the boundaries between the different localization modes. We establish this central result by using several one-dimensional slowly varying models, and reveal that the nonanalytic feature in the Lyapunov exponent is inherently tied to the singularities in the density of states through the Thouless formula. The possible existence of delicate structures in the localized phase effectively broadens our understanding of Anderson localization.

In this study we present a thorough theoretical and numerical investigation of the unified optical conductivity response in two-dimensional (2D) lattice systems that transition between the Lieb and kagome lattices through a tunable shear angle, $\varphi$. This continuous transformation enables us to analyze how optical properties evolve with lattice geometry. Our findings reveal that distinct interband transitions, either Dirac to Dirac and flat to Dirac, dominate at various structural stages, with the real longitudinal optical conductivity potentially reaching twice that of graphene (${\sigma }_0=\frac{e^2}{4\hslash }$) at a very low frequency. We establish that shear-induced structural changes lead to significant band hybridization while maintaining a low-frequency optical conductivity quantized at $2{\sigma }_0$. Sharp resonances arise in the finite-frequency regime due to strain-induced van Hove singularities. We also derive both real and imaginary components of optical conductivity, uncovering polarization-dependent plasmonic excitations, including TM-polarized modes in the low-frequency range (1–10 THz) and TE-polarized modes across a wider high-frequency window (65–240 THz) than seen in graphene and other 2D materials. These findings not only reinforce the physical relevance of flat bands and valley degeneracy but also highlight a feature of intraband conductivity under impurity-induced transitions. We explore intraband transitions in a distorted flat band during the Lieb-to-kagome lattice transformation, enabling a tunable low-frequency optical response. Our study combines analytical methods and numerical techniques, providing a platform to optimize the optical responses of tunable 2D lattices.

Non-Hermitian quantum systems, characterized by their ability to model open systems with gain and loss, have unveiled striking phenomena such as the non-Hermitian skin effect (NHSE), where eigenstates localize at boundaries under open boundary conditions. While extensively studied in noninteracting systems, the interplay between NHSE and strong electron correlations remains largely unexplored. Here, we investigate the non-Hermitian Hubbard model with asymmetric hopping, employing real-space dynamical mean-field theory (R-DMFT), a novel extension to such non-Hermitian correlated models—to capture both local correlations and spatial inhomogeneities. By analyzing the end-to-end Green's function as probes of directional amplification, we demonstrate that strong correlations can suppress the skin effect, leading to a crossover from boundary-dominated to correlation-driven dynamics. Our systematic study reveals that correlations dominate at small to intermediate strength of asymmetric hopping, inducing exponential decay in the end-to-end Green's function, but higher strength of asymmetric hopping can restore amplification even at strong interaction. These results illuminate the tunable interplay between correlations and non-Hermitian physics, suggesting avenues for engineering nonreciprocal transport in correlated open quantum systems.

Conventional ferroelectric tunnel junctions (FTJs) face inherent limitations in simultaneously achieving both a high tunneling electroresistance ratio (TER) and a low resistance-area product (RAP), hindering high-density, low-power, nonvolatile memory applications. This study overcomes this challenge by designing asymmetric FTJs based on a two-dimensional ${\mathrm{In}}_2{\mathrm{S}}_3/{\mathrm{Cu}}_2\mathrm{Se}$ heterostructure. Utilizing first-principles calculations with quantum transport simulations, we demonstrate that ferroelectric polarization switching in ${\mathrm{In}}_2{\mathrm{S}}_3$ reversibly modulates the heterostructure's band alignment between type-III (metallic) and type-II (semiconducting) states. Exploiting this, we engineered asymmetric ${\mathrm{In}}_2{\mathrm{S}}_3/{\mathrm{Cu}}_2\left({\mathrm{Se}}_{0.9}{\mathrm{S}}_{0.1}\right)$ and ${\mathrm{In}}_2{\mathrm{S}}_3/{\mathrm{Cu}}_2\left({\mathrm{Se}}_{0.9}{\mathrm{Te}}_{0.1}\right)$ electrodes flanking a central ${\mathrm{In}}_2{\mathrm{S}}_3/{\mathrm{Cu}}_2\mathrm{Se}$ barrier. The asymmetric FTJ achieves a TER of $9.95\times {10}^8\%$, which is 5 orders of magnitude higher than that of symmetric FTJs ($1.28\times {10}^3\%$), while maintaining an ultralow RAP of $0.11\mathrm{\Omega }\mu {\mathrm{m}}^2$. Crucially, these optimal performance metrics (TER $\sim {10}^9\%$, $\mathrm{RAP}<0.2\mathrm{\Omega }\mu {\mathrm{m}}^2$) persist robustly even under variations in channel width ($N=1$ to $N=9$, $\sim 0.7–6.3\mathrm{nm}$) or electrode doping concentration (5%–15%). These findings highlight the superior performance and exceptional robustness of the asymmetric ${\mathrm{In}}_2{\mathrm{S}}_3/{\mathrm{Cu}}_2\mathrm{Se}$-based FTJ, which holds significant promise for high-density, low-power, nonvolatile memory applications.

Motivated by the successful synthesis of isolated $\mathrm{Zr}{\mathrm{S}}_2$ and $\mathrm{Hf}{\mathrm{S}}_2$ transition metal dichalcogenide monolayers and inspired by their nearly identical lattice constants, we construct and investigate a vertical $\mathrm{Zr}{\mathrm{S}}_2/\mathrm{Hf}{\mathrm{S}}_2$ van der Waals (vdW) heterostructure. Using first-principles calculations based on density functional theory and many-body perturbation theory, we explore its electronic, optical, and excitonic properties, with particular emphasis on excitonic effects and temperature-dependent behavior. Based on the $\mathit{GW}$ method, the $\mathrm{Zr}{\mathrm{S}}_2/\mathrm{Hf}{\mathrm{S}}_2$ vdW heterostructure exhibits an indirect band gap of 2.60 eV with a type-I band alignment. The optical gap of the heterostructure is found to be 2.64 eV, with an exciton binding energy of 0.71 eV, both reduced compared to those in the isolated monolayers. We further investigate the temperature-dependent optoelectronic behavior of the heterostructure, considering electron-phonon coupling. A zero-point renormalization of 0.04 eV in the direct band gap is observed. While the direct band gap decreases monotonically with temperature from 0 to 400 K, the indirect band gap displays a nonmonotonic trend. As a result, the absorption spectrum undergoes a meaningful redshift with increasing temperature. At 300 K, the optical gap of the heterostructure is reduced to 2.51 eV and the exciton binding energy to 0.63 eV. Our findings highlight the important role of electron-phonon interaction in the optoelectronic response of $\mathrm{Zr}{\mathrm{S}}_2/\mathrm{Hf}{\mathrm{S}}_2$ vdW heterostructure, supporting its use in high-performance optoelectronic devices.

We show that a magnetic field parallel to the plane of a two-dimensional electron gas with Rashba spin-orbit coupling in proximity to a superconductor leads to a topological phase in coexistence with a single pair of Bogoliubov Fermi surfaces. This phase hosts antichiral edge states of copropagating Majorana fermions and are spatially localized at the opposite edges of the sample, perpendicular to the magnetic field. We discuss the characteristic signatures in the current-phase relation of a Josephson junction formed by two reservoirs in the topological phase.

Ordered crystalline compounds exhibiting ultralow and glasslike thermal conductivity are both fundamentally and technologically important, where phonon quasiparticles dominate their heat transport. Understanding the microscopic mechanisms that govern such unusual transport behavior is necessary to unravel the complex interplay of crystal structure, phonons, and collective excitations of these quasiparticles. Here, we use state-of-the-art first-principles calculations based on quantum density functional theory to investigate the origin of experimentally measured unusually low and glassy thermal conductivity in semiconducting TlAgTe that possesses disconnected chains of Tl atoms within its three-dimensional crystalline framework made up of distorted ${\mathrm{AgTe}}_4$ tetrahedra. Utilizing a unifying framework of anharmonic lattice dynamics theory that combine phonon self-energy induced frequency renormalization, particlelike Peierls (${\kappa }_l^P$), and wavelike coherent (${\kappa }_l^C$) thermal transport contributions, including three- and four-phonon scattering channels, we successfully explain the experimental results both in terms of magnitude and temperature dependence. Our analysis reveals that TlAgTe exhibits several localized phonon modes arising from concerted rattlinglike vibrations of Tl and Ag atoms, which show strong temperature dependence and enhanced four-phonon scattering rates that are dominated by Umklapp processes, suppressing ${\kappa }_l^P$ to ultralow values. The ensuing strong anharmonicity induced by local structural distortions, lone-pair electrons, and rattlinglike vibrations of the cations lead to a transition from particlelike behavior to wavelike tunneling (i.e., coherent) characteristics of the phonon modes above 40 ${\text{cm}}^{-1}$, contributing significantly to ${\kappa }_l^C$, which increases with temperature. Our analysis uncovers an important structure-property relationship, which may be used in designing materials with tunable thermal conductivity.

It is predicted by the Boltzmann transport equation (BTE) that the thermal conductivity of boron arsenide (BAs) at room temperature is as high as 1441 W/(m K). However, the experimental measurements exhibit striking variations, ranging from 53 to 2100 W/(m K). To reveal the divergence, high-precision neuroevolution potential (NEP) is first trained using density-functional theory (DFT) data and machine learning methods. Subsequently, NEP-based molecular dynamics (MD) simulations are used to investigate the growth mechanism of BAs, the formation and recombination of native defects, and lattice thermal conductivity. At 900 K, the formation enthalpy and cohesive energy for the cubic phase BAs are −0.017 and −5.38 eV, indicating that vapor B and As atoms can form the BAs phase instead of precipitating elemental phases B and As. At high temperatures, ${\mathrm{V}}_{\mathrm{B}}$, ${\mathrm{V}}_{\mathrm{As}}$, ${\mathrm{A}}_{\mathrm{B}}$, and ${\mathrm{A}}_{\mathrm{As}}$ exhibit low formation energy, suggesting that they may exist during crystal growth. Furthermore, we observe that ${\mathrm{A}}_{\mathrm{B}}\text{−}{\mathrm{A}}_{\mathrm{As}}$ pairs undergo recombination. Our investigation suggests that the ${\mathrm{A}}_{\mathrm{B}}\text{−}{\mathrm{A}}_{\mathrm{As}}$ pairs can be eliminated by reducing the cooling rate of the crystal, which provides guidance for crystal growth. Applying the homogeneous nonequilibrium molecular dynamics (HNEMD) approach, the thermal conductivity for defect-free BAs is predicted to be 1333 W/(m K). Due to defects scattering phonons, the thermal conductivity is suppressed to 44–208 W/(m K) for a system with a defect concentration of 1.40 $\times {10}^{20}{\mathrm{cm}}^{-3}$, which explains the underestimation of thermal conductivity in experimental measurements. This work establishes a pathway for identifying and understanding the functionality of defect suppression materials.

Frustrated magnets provide a platform for exploring exotic phases beyond conventional ordering, with potential relevance to functional materials and information technologies. In this work, we use Monte Carlo simulations to map the thermodynamic phase diagram of pyrochlore iridates $R_2{\mathrm{Ir}}_2{\mathrm{O}}_7$ ($R$ = Dy, Ho) with three stable magnetic ground-state phases: frustrated spin-ice 2-in–2-out phase, frustrated fragmented 3-in–1-out/1-in–3-out phase, and antiferromagnetic all-in–all-out phase without frustration. We investigate the physical origin of two enhanced-entropy (EE) phases at finite temperatures, which emerge at the boundaries between stable phases. These EE phases exhibit high magnetic susceptibility and high entropy without long-range order. Their stabilization arises from entropic minimization of the free energy, where the entropy dominates energetic competition near phase boundaries at finite temperatures. Our results demonstrate a platform to engineer highly susceptible and degenerated states through frustration and thermal activation, offering a foundation for the design of entropy-based materials and phases in correlated systems.

The studying of the interplay between magnetism and topology is crucial for understanding the fundamental physics of quantum materials and for developing next-generation electronic devices. Here, we investigate the emergence of half-metallic hybrid nodal chains (HMHNC) in ${\mathrm{YMnO}}_3$, revealing their unique topological properties and potential applications in spintronics. The HMHNC is formed by the intersection of multiple nodal lines protected by different symmetries, including glide mirror protected nodal lines and spin-group protected nodal lines. The HMHNC exhibits half-metallic behavior with approaching 100% spin polarization and is characterized by drumhead-shaped surface states, providing direct evidence for the existence of nodal semimetallic states. Furthermore, we reveal that the HMHNC provides a dominant contribution to the Berry curvature, thereby enhancing the anomalous transport properties. The anomalous Hall conductivity can be modulated by an external magnetic field, offering potential applications in spintronics. Our findings pave the way for further exploration of half-metallic nodal chains and their unique physical properties.

We analyze circular dichroism (CD) in resonant inelastic x-ray scattering (RIXS) in magnetic materials. We define RIXS-CD as the difference between scattering amplitudes for the right- and left-circularly polarized incoming photons and unpolarized (total) outgoing photons. We employ the impurity approximation, in which the interference between scattering events on different atoms is neglected. We perform a symmetry analysis of several common antiferromagnetic and altermagnetic structures and outline a general approach. This analysis is supported by numerical calculations using an atomic model with realistic crystal fields obtained from first principles. We show that RIXS-CD is distinguished from first-order spectroscopies such as x-ray magnetic circular dichroism by its insensitivity to the time-reversal symmetry breaking. As a result we find that RIXS-CD is present in the paramagnetic state of materials with lower symmetry. In antiferromagnets the RIXS-CD is invariant under Néel vector reversal. In altermagnets and ferromagnets the RIXS-CD spectra for time-reversed states are, in general, independent, except for the special case when there is a unitary symmetry of the Hamiltonian connecting the two states.

Altermagnetism provides new routes to realize Majorana zero modes with vanishing net magnetization. We consider a recently proposed heterostructure consisting of a semiconducting wire on top of an altermagnet and with proximity-induced superconductivity. We demonstrate that rotating the wire serves as a tuning knob to induce the topological phase. For $d$-, $g$-, and $i$-wave altermagnetic pairing, we derive angle-dependent topological gap-closing conditions. We derive symmetry constraints on angles where the induced altermagnetism must vanish, which we verify by explicit models. Our results imply that a bent or curved wire realizes a spatially-dependent topological invariant with Majorana zero modes pinned to positions where the topological invariant changes. This provides a new experimental set-up whereby a single wire can host both topologically trivial and nontrivial regimes without in situ tuning.

Metal-doped borophenes offer a versatile platform for realizing topological superconductivity and investigating exotic quantum states. In this study, through extensive structural searches, we identify the $t\text{-Be}{\mathrm{B}}_3$ monolayer and its stacked bilayer as the lowest-energy configurations within their respective layered systems. Compared to the monolayer, the ${\mathrm{AB}}^{\prime \prime }$-stacked bilayer forms interlayer Be-B covalent bonds that not only enhance thermodynamic stability but also drive a topological phase transition—resulting in the emergence of Dirac points and topological surface states near the Fermi level. Remarkably, the $p_z$ electrons localized on the interlayer Be-B bonds induce van Hove singularities and a flat band, which strongly couple to out-of-plane phonon modes. This leads to a significant enhancement in electron-phonon coupling (EPC) strength—from 0.51 in the $t{\text{-BeB}}_3$ monolayer to 0.85 in the bilayer—and yields a threefold increase in the superconducting critical temperature ($T_c$) from 10.3 to 30.2 K. These results highlight the pivotal role of interlayer bonding in tuning the electronic structure and EPC in borophene-based materials, offering a promising pathway toward the design of high-$T_c$ topological superconductors.