We investigate the temporal and spatial scales of resistance fluctuations ($R$ fluctuations) at the superconducting resistive transition accessed through voltage fluctuation measurements in thin epitaxial TiN films. This material is characterized by slow electron-phonon relaxation, which puts it far beyond the applicability range of the textbook scenario of superconducting fluctuations. The measured Lorentzian spectrum of the $R$ fluctuations identifies their correlation time, which is nearly constant across the transition region and has no relation to the conventional Ginzburg-Landau timescale. Instead, the correlation time coincides with the energy relaxation time determined by a combination of the electron-phonon relaxation and the relaxation via diffusion into reservoirs. Our data are quantitatively consistent with the model of spontaneous temperature fluctuations and highlight the lack of understanding of the resistive transition in materials with slow electron-phonon relaxation.

We present an analysis of the half-filled CPT model, an analytically tractable Kondo lattice model with Yao-Lee spin-spin interactions on a 3D hyperoctagon lattice, proposed by Coleman, Panigrahi, and Tsvelik. Previous studies have established that the CPT model exhibits odd-frequency triplet superconductivity and order fractionalization. Through asymptotic analyses in the small-$J$ and large-$J$ Kondo coupling limits, we identify a quantum critical point at $J_c$, marking a transition from a superconductor to a Kondo insulator. By estimating the vison gap energy to account for thermal gauge fluctuations, we determine the energy scales governing the thermal breakdown of order fractionalization. Moreover, at large $J$ the Kondo insulator undergoes orbital decoupling, leading to the formation of a decoupled Kitaev orbital liquid. These findings and analogies with the ${\mathbb{Z}}_2$-gauged $XY$ model lead us to propose a tentative phase diagram for the CPT model at half-filling.

Hedin's equations provide an elegant route to compute the exact one-body Green's function (or propagator) via the self-consistent iteration of a set of nonlinear equations. Its first-order approximation, known as $GW$, corresponds to a resummation of ring diagrams and has shown to be extremely successful in physics and chemistry. Systematic improvement is possible, although challenging, via the introduction of vertex corrections. Considering anomalous propagators and an external pairing potential, we derive a self-consistent set of closed equations equivalent to the famous Hedin equations but having as a first-order approximation, the particle-particle (pp) $T$-matrix approximation, where one performs a resummation of the ladder diagrams. This pp version of Hedin's equations offers a way to go systematically beyond the $T$-matrix approximation by accounting for low-order pp vertex corrections.

The introduction of Peierls phases in open tight-binding chains without closed paths in either real or synthetic dimensions is understood to be physically inconsequential, as one assumes they can always be gauged away. Here, we show that this assumption does not necessarily hold for all systems in open chains, as closed paths may appear in the Fock space where these phases can lead to the creation of magnetic flux analogs with physical effects. This idea is first illustrated in the quadratic Kitaev model, where different patterns for the Peierls phases are studied and their independent manipulation is seen to be able to drive the appearance of topological states and Majorana flat bands. We then consider a system with quartic interactions, namely an extended Bose-Hubbard (EBH) open chain with a finite Peierls phase associated with the hopping terms. Focusing on the strong interactions limit of the two-body sector, we show the decisive influence of these phases on the two-band spectrum of the higher energy subspace, which behaves as an effective sawtooth chain with magnetic flux at each plaquette. In particular, both the width of the energy gap between the two bands and the position of the in-gap edge states can be controlled by the Peierls phase. Finally, by translating this two-particle one-dimensional (1D) system into a single-particle two-dimensional (2D) one, and subsequently mapping it onto an equivalent electrical LC circuit, we identify a parameter set for which in-gap states are only present for certain finite phase values. Tuning the circuit to these parameters generates the corresponding boundary voltage states, providing an experimentally detectable signature of the effects induced by manipulating Peierls phases in a model built on an open linear chain.

We investigate theoretically a one-dimensional semiconductor-superconductor (SM-SC) heterostructure with Rashba spin-orbit coupling and parallel Zeeman field in the presence of disorder generated by random charged impurities and identify the optimal regimes for realizing topological superconductivity and Majorana zero modes. Using a Green's function approach, we show that upon increasing the disorder strength the stable topological superconducting phase characterized by robust end-to-end Majorana correlations “migrates” toward larger values of the Zeeman field and can be stabilized by increasing the effective SM-SC coupling. Based on these findings, we propose a strategy for accessing a regime characterized by well-separated Majorana zero modes that is based on (a) enhancing the strength of the effective SM-SC coupling (e.g., through interface engineering) and (b) expanding the range of accessible Zeeman fields (e.g., by enhancing the gyromagnetic ratio or optimizing the parent superconductor, to enable the application of larger magnetic fields). While this strategy may still require some reduction of the disorder strength, this requirement is significantly less strict than the corresponding requirement in a strategy that focuses exclusively on disorder reduction.

Heat transfer at the interface between two materials is becoming increasingly important as the size of electronic devices shrinks. Most studies concentrate on the interfacial thermal conductance between either crystalline-crystalline or amorphous-amorphous materials. Here, we investigate the interfacial thermal conductance at crystalline-amorphous interfaces using nonequilibrium molecular dynamics simulations. Specifically, gold and two different materials, silicon and silica, in both their crystalline and amorphous structures, have been considered. The findings reveal that the interfacial thermal conductance between amorphous structures and gold is significantly higher as compared with crystalline structures for both planar and rough interfaces ($\approx 152\mathrm{MW}/\left({\mathrm{m}}^2\mathrm{K}\right)$ for gold-amorphous silicon and $\approx 56\mathrm{MW}/\left({\mathrm{m}}^2\mathrm{K}\right)$ for gold-crystalline silicon). We explain this increase by two factors: the relative commensurability between amorphous silicon or silica and gold leads to enhanced bonding and cross correlations of atomic displacements at the interface, contributing to enhance phonon elastic transmission. Inelastic phonon transmission is also enhanced due to the relative larger degree of anharmonicity characterizing gold-amorphous silicon or silica. We also show that all the vibrational modes that participate to interfacial heat transfer are delocalized and use the Ioffe-Regel (IR) criterion to separate the contributions of propagating (propagons) and nonpropagating modes (diffusons). In particular, we demonstrate that, while at gold-amorphous silicon interfaces elastic phonon scattering involves propagons and inelastic phonon scattering involves a mixture of propagons and diffusons, in gold-amorphous silica, all modes transmitting energy at the interface are diffusons. This study calls for the systematic experimental determination of the interfacial thermal conductance between amorphous materials and metals.

Critical phenomena beyond the Landau-Ginzburg-Wilson paradigm have been long sought after. Among many candidate scenarios, the deconfined quantum critical point (DQCP) constitutes the most fascinating one, and its lattice model realization has been debated over the past two decades. Following pioneering works with the fuzzy sphere methods [Zhu et al., Phys. Rev. X 13, 021009 (2023); Hu et al., Phys. Rev. Lett. 131, 031601 (2023); Han et al., arXiv:2312.04047; Zhou et al., Phys. Rev. X 14, 021044 (2024)], we apply the spherical Landau level regularization to study the effective $(2+1)\mathrm{D}$ SO(5) nonlinear sigma model with a topological term and the potential DQCP therein. Utilizing the state-of-the-art density matrix renormalization group method with explicit ${\text{SU(2)}}_{\text{spin}}\times {\text{U(1)}}_{\text{charge}}\times {\text{U(1)}}_{\text{angular-momentum}}$ symmetry as well as exact diagonalization simulations, we provide a comprehensive phase diagram for the model with a SO(5) continuous transition line—extension of the previous identified SO(5) multicritical point [Chen et al., Phys. Rev. Lett. 132, 246503 (2024)]—while tuning interaction length. The state-operator correspondence with the conformal tower structure is used to identify the emergent conformal symmetry with the best scaling dimension of relevant primary fields, and they match well with the critical exponents obtained from the crossing point analysis of the correlation ratio. Our results thus further support the rich structure of the phase diagram of the SO(5) model.

Long-wavelength spin fluctuations prohibit antiferromagnetic long-range order at finite temperature in two dimensions. Nevertheless, the correlation length starts to grow rapidly at a crossover temperature, leading to critical slowing down and to a renormalized-classical regime over a wide range of temperature, between a fraction of the mean-field transition temperature and the zero-temperature ordered state. This leads to a single-particle pseudogap of the kind observed in electron-doped cuprates. Very few theoretical methods can claim an accurate description of this regime. The challenge is that in this regime Fermi-liquid quasiparticles are already destroyed and new quasiparticles of the ordered state are not fully formed yet. Here, we study this problem for the two-dimensional Hubbard model by first generalizing the two-particle self-consistent approach. Using a special algorithm, spin fluctuations are treated in the thermodynamic limit even for large correlation lengths. The effects of Kanamori-Brückner screening, of classical and of quantum fluctuations are taken into account. Results are presented at half filling for the one-band Hubbard model with nearest-neighbor hopping. They agree well with available benchmark diagrammatic quantum Monte Carlo at high temperature where the pseudogap opens up. In addition to temperature-dependent spectral properties, we find quantum corrections to the zero-temperature renormalized mean-field antiferromagnetic gap. Finally, analytic continuation of the Matsubara results for spectral functions show that the pseudogap opens up at significantly higher temperature than was previously identified based on the Matsubara data only.

We develop the theory for dynamics of the out-of-plane deformations in flexible two-dimensional materials. We focus on study of attenuation of flexural phonons in free-standing crystalline membranes. We demonstrate that the dynamical renormalization does not involve the ultraviolet divergent logarithmic contributions contrary to the static ones. This fact allows us to find the scaling form of the attenuation, determine its small- and large-frequency asymptotes, and to derive the exact expression for the dynamical exponent of flexural phonons in the long-wave limit: $\mathsf{\text{z}}=2-\eta /2$. Here $\eta$ is the universal exponent controlling the static renormalization of the bending rigidity. Also we determine the dynamical exponent for the long-wave in-plane phonons: ${\mathsf{\text{z}}}^{\prime }=(2-\eta /2)/(1+\eta /2)$. We discuss implication of our results to experiments on phonon spectra in graphene and dynamics of graphene-based nanomechanical resonators.

Higher-order topological corner states have been realized in a two-dimensional Kekulé lattice, which can be further coupled with spin polarization through the implementation of local magnetization. In this paper, we numerically investigate the spin-dependent transport properties assisted by topological corner states in the Kekulé lattice. By applying local magnetization and an electric potential, the topological corner states are spin polarized with opposite spins localized at different corners, thereby demonstrating a spin-corner state locking mechanism. Transport characteristics, including transmission, local density of states, and local current density, are calculated for a two-terminal setup consisting of a diamond-shaped Kekulé lattice connected to two leads. When opposite local magnetization is applied to the corners, spin-up and spin-down electrons are perfectly separated, forming two spin-polarized conducting channels and leading to spin spatial separation. In the presence of identical local magnetization on both corners and an electric potential at one corner, the spin-polarized corner states can facilitate selective filtering of different spins and generate spin-polarized currents by tuning the energy. Furthermore, spin-resolved transmission diagrams as functions of both the Fermi energy and electric potential are presented, illustrating the global distribution of spin filtering through topological corner states.

Two-dimensional (2D) ferroelectricity with switchable electric polarization has drawn widespread attention in condensed matter physics due to its crucial applications in nonvolatile memory and ferroelectric spin devices. Despite recent progress in 2D ferroelectricity, achieving monoelemental (ME) ferroelectricity still remains a great challenge because most nonmetallic ME materials are stabilized in nonpolar crystal structures. In this work, we theoretically designed ME ferroelectricity with tunable and significant spin textures in bilayer tellurium (BL-Te). Comprehensive polarization calculations demonstrate that asymmetric stacking in BL-Te can generate out-of-plane (OOP) polarization with a magnitude of 0.49 pC/m. This polarization stems from distinguishing interlayer and intralayer contributions. Moreover, these stacked BL-Te, characterized by significant spin-orbit coupling, serve as an ideal platform for investigating both conventional spin polarization and layer-dependent/hidden spin polarization through ferroelectric reversion. Our work not only broadens the family of 2D ME ferroelectrics but also offers a new platform for multifunctional nanodevices.

X-ray laser-induced structural changes in silicon undergoing femtosecond melting have been investigated by using an x-ray pump–x-ray probe technique. The experiment reveals that the atomic displacements start to increase at $\sim 20$ fs after the intensity maximum of x-ray pump pulse. By comparing the observed time dependence of the atomic disordering and the dedicated theoretical simulations, we interpret that the energy transfer from the excited electrons to ions via electron-ion coupling (thermal effect) as well as a strong modification of the interatomic potential due to electron excitations (nonthermal effect) trigger the ultrafast atomic disordering. Our results highlight the need to consider the interplay of thermal and nonthermal effects in the quantitative modeling of the interaction of intense x rays with matter.

We report the synergy between orbital and spin-orbit torques in ${\mathrm{WTe}}_2/{\mathrm{Fe}}_3{\mathrm{GeTe}}_2$ heterostructures characterized by a Berry curvature dipole. By applying a current along the $a$ axis in ${\mathrm{WTe}}_2$, we detect an out-of-plane magnetization in the system, which we attribute to nonequilibrium orbital magnetization linked to the Berry curvature dipole based on first-principles calculations, manifesting as the orbital Edelstein effect. This effect generates orbital torques that enable field-free perpendicular magnetization switching. Furthermore, by applying a relatively small current along the $a$ axis and a pulsed current along the $b$ axis in ${\mathrm{WTe}}_2$, we demonstrate controllable field-free magnetization switching of the adjacent ${\mathrm{Fe}}_3{\mathrm{GeTe}}_2$ layer, independently manipulating the orbital and spin-orbit torques. Our findings not only enhance the understanding of the collaborative dynamics between these torques but also suggest potential applications in magnetoresistive random-access memory.

Density matrix renormalization group (DMRG) or matrix product states (MPS) is the most effective and accurate method for studying one-dimensional quantum many-body systems. However, the application of DMRG to two-dimensional systems is not as successful because of the limited entanglement encoded in the wave-function ansatz. The fully augmented matrix product states (FAMPS), introduced recently in [Chin. Phys. Lett. 40, 057102 (2023)], extends MPS formalism to two dimensions and increases the entanglement in the wave-function ansatz, representing a significant advance in the simulation of two-dimensional quantum many-body physics. In the study of one-dimensional systems, the concept of a parent Hamiltonian for MPS has proven pivotal in the understanding of quantum entanglement. In this work, we extend this framework to two-dimensional systems. We illustrate the procedure to construct a two-dimensional Hamiltonian with given FAMPS as its exact ground state (the parent Hamiltonian for FAMPS). Additionally, through numerical simulations, we demonstrate the effectiveness of the algorithm outlined in [Chin. Phys. Lett. 40, 057102 (2023)] in precisely identifying the FAMPS for the constructed parent Hamiltonian. The introduction of FAMPS and its associated parent Hamiltonian provides a useful framework for the future investigations of two-dimensional quantum many-body systems.

The behavior of surface waves in a soil supporting an array of beams in three dimensions, or an array of plates in two dimensions, with compressional and flexural resonances is examined both theoretically and numerically. Our findings demonstrate that Love waves, characterized by displacements perpendicular to the sagittal plane, can propagate even without a homogeneous guiding layer, owing to the influence of flexural resonances in beams. Within the sagittal plane, hybridized Rayleigh waves exhibit a dispersion that is notably altered by the presence of the array, with their properties emerging from the interaction between flexural and compressional resonances. Notably, we uncover the coexistence of two Rayleigh waves with distinct wave numbers within specific frequency ranges, corresponding to prograde and retrograde motions. Additionally, both waves significantly amplify ground motion, either horizontally or vertically. Similar physics, yet quantitatively different, is demonstrated in the case of plate arrays.

As a member of noble gas, xenon behaves complexly, especially under pressure. Hypervalent xenon compounds under extreme conditions offer the potential to probe the intrinsic physical and chemical properties of Xe and also give answers to the missing Xe paradox. Therefore, we theoretically explored the ternary phase diagrams of the Xe-C-O system under high pressures and identified two stable hypervalent compounds, $I\overline{4}\text{−}\mathrm{XeC}{\mathrm{O}}_4$ and $P{6}_{3}mc\text{−}{\mathrm{Xe}}_2\mathrm{C}{\mathrm{O}}_4$ at 100 and 200 GPa, respectively, where the coordination number of the Xe atom increases from 4 to 16 as pressure increases. The bonding mechanism of ${\mathrm{Xe}}_2\mathrm{C}{\mathrm{O}}_4$ is different from the three-center–four-electron bonds observed in $\mathrm{XeC}{\mathrm{O}}_4$, which is the pressure-induced $s{p}^3$ hybridization of $\mathrm{X}{\mathrm{e}}^{2+}$ with half-filled antibonding orbitals that overlap with the nonbonding orbitals of oxygen in the $\mathrm{C}{\mathrm{O}}_4$ unit. The ab initio molecular dynamics calculations show that these two compounds maintain solid states under the extreme conditions corresponding to the interior regions of the Earth. These findings reveal the bonding mechanism of unexpected hypervalent compounds involving the noble element Xe and potentially provide important support for the explanation of the storage of xenon in Earth.

We study hyperuniform properties for the square-triangle tilings. The tiling is generated by a local growth rule, where squares or triangles are iteratively attached to its boundary. The introduction of the probability $p$ in the growth rule, which controls the expansion of square and triangle domains, enables us to obtain various square-triangle random tilings systematically. We analyze the degree of the regularity of the point configurations, which are defined as the vertices on the square-triangle tilings, in terms of hyperuniformity. It is clarified that for $p<p_c(p_c\sim 0.5)$, the system can be regarded as a phase separation between square and triangular lattice domains and the variance of the point configurations obeys the scaling law ${\sigma }^2\sim O\left(R^{2-\alpha }\right)$ with $\alpha <0$. The configurations are antihyperuniform. On the other hand, for $p>p_c$, the squares and triangles are spatially well mixed and the point configurations belong to the hyperuniform class III with the exponent $0<\alpha <1$. This means the existence of the hyperuniform-antihyperuniform transition at $p=p_c$. We also examine the structure factor of the square-triangle tilings. It is clarified that the peak structures in the large-wave-number regime are mostly common to all square-triangle tilings, while those in the small-wave-number regime strongly depend on whether the point configurations are hyperuniform or antihyperuniform.

Infinite projected entangled-pair states (iPEPS) provide a powerful tool to study two-dimensional strongly correlated systems directly in the thermodynamic limit. In this work, we extend the iPEPS toolbox by a method to efficiently evaluate nonequal time two-point correlators, enabling the computation of spectral functions. It is based on an iPEPS ansatz of the ground state in a large unit cell, with an operator applied in the center of the cell, which is evolved in real-time using the fast-full update method. At every time step, the two-point correlators within a cell are computed based on the corner transfer matrix renormalization group method. Benchmark results for the two-dimensional transverse field Ising model show that the main features of the dynamical structure factor can already be reproduced at relatively small bond dimensions and unit cell sizes. The results for the magnon dispersion are found to be in good agreement with previous data obtained with the iPEPS excitation ansatz.

We study the equilibrium properties of the spin-$1/2$ XY chain with an infinite-range transverse interaction. At zero temperature, competition between the XY- and $z$-ordered phases induced by the infinite-range interactions gives rise to a first-order transition upon increasing the transverse coupling. We show that the two gapless points of the XY model behave in fundamentally different ways: isotropic spin chains experience a first-order transition at finite coupling; maximal anisotropic chains overcome a nonalgebraic phase transition at zero coupling strength. The phase diagram depicts a first-order reentrant transition that turns second order along a tricritical line separating a paramagnetic phase from an ordered one at finite temperature. The mean-field approach captures the local properties of the eigenstates and reveals the appearance of a magnetization gap in the spectrum. Global properties, e.g., entanglement entropy, are well approximated only at spectral boundaries. The mean entanglement entropy and the level-spacing ratio deviate from the Gaussian results, revealing the interacting nature of the problem.