Twisted bilayer graphene (T-BLG) has emerged as a compelling platform for investigating novel physical phenomena through moiré superlattices. Its exceptional electrical, magnetic, optical, and topological characteristics make it particularly promising for thermal management and thermoelectric applications. In this work, we present a systematic first-principles study comparing the two-channel thermal transport mechanisms between AB-stacked bilayer graphene (AB-BLG) and T-BLG, with a focus on higher-order phonon transport and electron-phonon coupling effects. Our results reveal that high-order anharmonicity significantly suppresses thermal conductivity in both systems, with a more pronounced effect in AB-BLG (42.0% reduction) compared to T-BLG (34.6% reduction) at 300 K. The enhanced four-phonon scattering in AB-BLG manifests as more distinct higher-order polynomial characteristics in quadratic residuals, primarily due to elevated four-phonon scattering rates within the low-frequency region ($0\sim 10\mathrm{THz}$). Notably, T-BLG exhibits distinctive wavelike phonon transport characteristics, contributing 6% to the total thermal conductivity at 300 K and approaching 10% at temperatures above 600 K, while such effects remain negligible in AB-BLG. Moreover, electron-phonon interactions (EPI) dramatically influence thermal transport, particularly in T-BLG, where $p$-type doping (3 × ${10}^{15}\mathrm{c}{\mathrm{m}}^{-2}$) induces an 81.9% reduction in thermal conductivity, far exceeding the 31.0% reduction observed in AB-BLG. We attribute the enhanced electron-phonon coupling in T-BLG to its unique electronic band structure, characterized by stronger intervalley scattering, higher density of states near the Fermi level, and structural intrinsic disorder. Moreover, the stronger EPI effect in T-BLG is attributed to a broader spatial distribution enabled by symmetry breaking, which activates more scattering channels despite weaker average coupling strength. EPI also significantly suppresses the phonon coherence in AB-BLG and T-BLG. When the carrier concentration is at the maximum value of the electron density of states, the wavelike thermal conductivity reaches its minimum, and the suppression effect of the electron-phonon coupling on phonon coherence is strongest. These insights elucidate the distinct thermal transport mechanisms in bilayer graphene systems and suggest potential strategies for thermal conductivity modulation through twist angle engineering.

Recent advances in superconducting circuit technology have made the fabrication of large, customizable circuits routine. This has led to applications beyond quantum information, including quantum simulation. A key challenge in this effort is the identification of the quantum states realized. Here, we propose a probe circuit capable of measuring many-body correlations in an analog quantum simulator superconducting circuit. This probe, which is specially designed for many-photon states, exploits the nonlinearity of the Josephson junction to measure two-point correlation functions of the superconducting phase operator. We demonstrate the capabilities of this design in the context of an LC-ladder with a quantum impurity. The proposed probe allows for the measurement of inherently quantum correlations, such as two-mode squeezing, and it has the potential to significantly expand the scope of analog quantum simulations using superconducting circuits.

We study the behavior of magic as a bipartite correlation in the quantum Ising chain across its quantum phase transition and at finite temperature. To quantify the magic of partitions rigorously, we formulate a hybrid scheme that combines stochastic sampling of reduced density matrices via quantum Monte Carlo, with state-of-the-art estimators for the robustness of magic - a bona fide measure of magic for mixed states. This allows us to compute the mutual robustness of magic for partitions up to eight sites, embedded into a much larger system. We show how mutual robustness is directly related to critical behaviors: at the critical point, it displays a power-law decay as a function of the distance between partitions, whose exponent is related to the partition size. Once finite temperature is included, mutual magic retains its low temperature value up to an effective critical temperature, whose dependence on size is also algebraic. This suggests that magic, differently from entanglement, does not necessarily undergo a sudden death.

Two-dimensional compensated antiferromagnets (AFMs) offer unique advantages for spintronics, yet their vanishing net magnetization makes direct electrical readout challenging. Here, we demonstrate that the anomalous Hall effect (AHE) can be realized in AFM MnS through two mechanisms: application of a vertical electric field or interlayer sliding ferroelectricity, both of which break spatial inversion symmetry $\mathcal{P}$ and the combined space-time inversion symmetry $\mathcal{PT}$. In monolayer and AA-stacked bilayer MnS, a sizable anomalous Hall conductivity (AHC) emerges under an applied electric field, with its sign reversing upon reversal of either the Néel vector or the field direction. In sliding-modified ${\mathrm{AB}}^{\prime }$-stacked bilayer MnS, broken symmetries give rise to robust out-of-plane polarization and spontaneous AHE, where polarization reversal induced by sliding simultaneously flips the AHC. These results establish a direct coupling between the AHE, AFM order, and ferroelectric polarization, providing a practical route toward electrical readout and information storage in two-dimensional AFM spintronic devices.

Kagome quantum materials, with their frustrated lattice geometry and flat-band electronic structure, serve as a versatile platform for studying magnetism and electron correlation. The recently discovered kagome metal ${\mathrm{CsCr}}_3{\mathrm{Sb}}_5$ has garnered significant interest for its coexistence of multiple orders and the emergence of pressure-induced superconductivity. In this study, we theoretically investigate the correlation effects on the electronic structures and magnetism of ${\mathrm{CsCr}}_3{\mathrm{Sb}}_5$. Based on our proposed effective tight-binding model, we reveal orbital-selective correlation effects that induce a near-flat band just below the Fermi level, consistent with recent experimental observations. By combining the symmetry analysis and second-order perturbation theory, we construct an effective spin model and thoroughly explore its classical phase diagram, suggesting that a special $q=0$ state might correspond to the magnetic order in ${\mathrm{CsCr}}_3{\mathrm{Sb}}_5$. Our findings highlight the electron correlations in ${\mathrm{CsCr}}_3{\mathrm{Sb}}_5$ and provide novel insights into its magnetic properties. Furthermore, this spin model is applicable to kagome materials with similar structures, making the complete phase diagram relevant to other similar systems as well.

Direct radiative recombination of high excited confined states across the band gap is observed as a broad emission band above the InGaN band edge in photoluminescence and electroluminescence for wide InGaN quantum wells (QWs). The observation of hot carrier interband recombination is possible in wide InGaN quantum wells because the transitions between the lower lying confined states are spatially indirect due to the piezoelectric field, and therefore become dark states with extremely low radiative transition rates at low carrier densities. Hot carrier luminescence was observed consistently for 7.8- and $25\text{−}\mathrm{nm}$-wide QWs at low and room temperature, while it is absent for a $2.6\text{−}\mathrm{nm}$-thin QW. The spectrum of the emission is explained by $k·p$ simulations assuming a weak dependency of the transition matrix element on the subband of the confined states, and a limited extent of carrier momentum around the $\mathrm{\Gamma }$ point.

Recent experiments have demonstrated efficient spin transfer across layers in the van der Waals heterostructure composed of ${\mathrm{WTe}}_2$ and ${\mathrm{Fe}}_3{\mathrm{GeTe}}_2$, signaling a potential breakthrough in developing all–van der Waals spin-orbit torque devices. However, the reasons behind the unusually high interlayer spin transparency observed, despite the weak van der Waals interactions between layers, remain unclear. In this study, we employ density functional theory and the nonequilibrium Green's function method to explore this phenomenon. We find that the efficient cross-layer spin transfer arises from direct hybridization of $p$-orbitals between tellurium atoms at the interface. This interlayer orbital hybridization lowers the electronic potential barrier and significantly modifies the spin-polarized electronic structure of ${\mathrm{Fe}}_3{\mathrm{GeTe}}_2$. Consequently, an effective channel for spin-polarized transport is established between ${\mathrm{WTe}}_2$ and ${\mathrm{Fe}}_3{\mathrm{GeTe}}_2$, leading to high interlayer spin transparency. Combining this enhanced spin transparency with the large spin Hall angle of ${\mathrm{WTe}}_2$ explains the high spin-orbit torque efficiency observed experimentally. Furthermore, we predict that applying a gate voltage can further increase this efficiency. Our findings offer a pathway for designing high-performance, all–van der Waals spin-orbit torque devices.

We establish a unified framework for dynamical quantum phase transitions (DQPTs) in non-Hermitian systems that encompasses both biorthogonal and self-norm nonbiorthogonal formulations for pure and mixed states under quantum quench protocols. Our framework provides explicit expressions for the Loschmidt amplitude, Loschmidt echo, and rate function, revealing a universal geometric signature of DQPTs in the two-band model: orthogonality of two related vectors in two-dimensional real space. Strikingly, we demonstrate that nonbiorthogonal quenches from non-Hermitian to Hermitian Hamiltonians under chiral symmetry exhibit emergent topological characteristics of DQPTs, unveiling their fundamental features beyond conventional Hermitian regimes. This work establishes fundamental geometric and topological principles governing quantum criticality in open systems, with implications for quantum sensing and many-body physics in dissipative environments.

Spin-$\frac{1}{2}$ Heisenberg antiferromagnetic frustrated spin-chain systems display exotic ground states with unconventional excitations and distinct quantum phase transitions as the ratio of next-nearest-neighbor to nearest-neighbor coupling is tuned. We present a comprehensive investigation of the structural, magnetic, and thermodynamics properties of the spin-$\frac{1}{2}$ compound, $\mathrm{Cu}\text{(Ampy)ClBr}(\text{Ampy}={\mathrm{C}}_6{\mathrm{H}}_8{\mathrm{N}}_2=2$-(aminomethyl)pyridine) via x-ray diffraction, magnetization, specific heat, ${}^1\mathrm{H}$ nuclear magnetic resonance (NMR), electron spin resonance, and muon spin relaxation ($\mu \mathrm{SR}$) techniques. The crystal structure features an anisotropic triangular chain lattice of magnetic ${\mathrm{Cu}}^{2+}$ ions. Our bulk and local probe experiments detect neither long-range magnetic ordering nor spin freezing down to 0.06 K despite the presence of moderate antiferromagnetic interaction between ${\mathrm{Cu}}^{2+}$ spins as reflected by a Curie-Weiss temperature of about $-9\mathrm{K}$ from the bulk susceptibility data. A broad maximum is observed at about 9 K in magnetic susceptibility and specific-heat data, indicating the onset of short-range spin correlations. At low temperatures, the zero-field magnetic specific heat and the ${}^1\mathrm{H}$ NMR spin-lattice relaxation rate follow an exponential temperature dependence, indicating the presence of gapped magnetic excitations. Furthermore, persistent spin dynamics down to 0.088 K observed by zero-field $\mu \mathrm{SR}$ evidences lack of any static magnetism.

In this work, the electronic structure, the uniform magnetic susceptibility, and the static and dynamic local magnetic susceptibilities of $\delta$-Pu are investigated with the help of density functional theory (DFT) plus dynamical mean-field theory. Consistent with experimental observations and at variance with DFT, the ground state at low temperature is found to be nonmagnetic and characterized as a mixed-valence system, where the local magnetic moment from the partially filled $5f$ shell is effectively screened by the conduction electrons. Importantly, as the temperature rises a local magnetic moment emerges with antiparallel orbital and spin angular momenta, leading to a transition from a Pauli-like behavior to an apparent weak Curie-Weiss magnetism in the uniform magnetic susceptibility. The crossover regime corresponds to the emergence of a local moment as evidenced by the local susceptibilities. This finding reconciles previous discrepancies between experimental observation and theoretical simulations.

The two-dimensional (2D) altermagnet (AM) is regarded as a promising candidate to achieving spintronic and valleytronic devices due to its large nonrelativistic spin splitting and high-density integration. It is crucial to explore the manipulation mechanism of spin, valley polarization, and piezoelectric response in the 2D AM system. We perform first-principles calculations to study monolayer ${\mathrm{Co}}_2{\mathrm{MoSe}}_4$ and find that it is an AM semiconductor with a Néel temperature of $\sim$84 K. The ${\mathrm{Co}}_2{\mathrm{MoSe}}_4$ monolayer has a 0.97 eV direct band gap located at the X/Y valley, and the valley degeneracy is protected by the crystal symmetry. Furthermore, this monolayer exhibits large spin splittings of 0.53 and 0.45 eV for the valence and conduction bands, respectively. Our calculations reveal that uniaxial strain could give rise to significant valley polarization and asymmetric distributions of Berry curvature due to the diagonal mirror symmetry breaking. It is predicted that the strain-driven magnetic response switching characterized with nonzero net magnetization can be realized by using hole doping combined with an in-plane strain. This monolayer is expected to be an excellent shear-type piezoelectric candidate with an impressive piezoelectric coefficient. The monolayer could exhibit the multipiezo effect induced by uniaxial strain, including the piezoelectricity, piezovalley, piezomagnetism, and anomalous valley Hall effect. Our findings provide not only a perspective for exploring the versatility of the 2D AM but also a platform to develop next-generation multifunctional devices.

We study the one-dimensional extended Hubbard model coupled with an optical cavity, which describes an interplay of the effect of vacuum fluctuation of light and the quantum phase transition between the charge- and spin-density-wave phases. The ground state and excitation spectrum of the model are calculated by numerically exact tensor-network methods. We find that the photon number of the ground state is enhanced (suppressed) along the quantum phase transition line when the light-matter coupling is comparable to (much smaller than) the cavity frequency. We also show that the exciton peak in the optical conductivity and single photon excitation peak in the photon spectrum exhibit the vacuum Rabi splitting at resonance due to the light-matter interaction. This behavior is in contrast to the case without excitons, where the photon spectrum is merely broadened without splitting due to the lack of a sharp resonance.

Recent work on Abelian topological phases with rotational symmetry has raised the question of whether rotational symmetry can protect gapless propagating edge modes. Here we address this issue by considering the coupling of topological phases to the extrinsic geometry of the background. First, we analyze an effective hydrodynamic theory for an Abelian topological phase with vanishing Hall conductance. After integrating out the bulk hydrodynamic degrees of freedom, we identify charge neutral, rotationally invariant-mass terms by coupling the propagating boundary modes to the extrinsic geometry. This allows us to integrate out the edge modes and we find a gapped theory described by a local induced action that depends on the extrinsic geometry of the boundary, regardless of the shift. Finally, we apply these ideas to a microscopic theory and find the explicit bulk terms which respect gauge and rotational symmetry and open a gap in the edge spectrum.

The interaction model of two electrons in the edge states of a two-dimensional topological insulator is investigated. Both solutions of the Schrödinger equation and solutions of the Bethe-Salpeter equation at different values of the Fermi energy are considered. It is shown that for the Bethe-Salpeter equation, which takes into account the existence of the Fermi surface, there is a discrete spectrum in the system of two electrons. This phenomenon does not appear in the case of the Schrödinger equation. We found the bound-state energy for nonzero total momentum of electrons.

It is well known that the standard bulk-boundary correspondence does not hold for non-Hermitian systems in which also new phenomena such as exceptional points occur. Here, we study, mostly by analytical means, a paradigmatic one-dimensional non-Hermitian model with dimerization, asymmetric hopping, and imaginary staggered potentials. We present analytical solutions for the singular value and the eigensystem of this model with both open and closed boundary conditions. We explicitly demonstrate that the proper bulk-boundary correspondence is between topological winding numbers in the periodic case and singular values, not eigenvalues, in the open case. These protected singular values are connected to hidden edge modes that only become exact zero-energy eigenmodes in the semi-infinite chain limit. We also show that a nontrivial topology leads to protected eigenvalues in the entanglement spectrum. In the $\mathcal{PT}$-symmetric case, we find that the model has a previously overlooked phase where exceptional points become dense in the thermodynamic limit. This phase shows unusual hyper-ballistic transport properties with a dynamical critical exponent $z=1/2$.

Sliding ferroelectrics, which exhibit out-of-plane polarization arising from specific stacking rather than conventional ionic displacements, are new types of ferroelectrics whose underdeveloped physics needs to be explored. Here, we investigate the electro-optic (EO) response of these materials using first-principles calculations, focusing on ${\mathrm{ZrI}}_2$ as a prototype. We reveal that, contrary to conventional ferroelectrics, the EO effect in ${\mathrm{ZrI}}_2$ is dominated by its electronic contribution rather than the ionic one, which promises faster EO responses. Furthermore, both biaxial and uniaxial strains significantly enhance this response, and a universal-like linear relationship between the band gap and such response is discovered. We also report a large elasto-optic coefficient that is independent of biaxial strain. Similar large linear EO coefficients and properties are found in other sliding ferroelectrics, including different zirconium dihalides, as well as BN and BP bilayers. These findings highlight sliding ferroelectrics as highly promising candidates for ultrafast nonlinear optical devices and reveal unusual EO mechanisms.

The normal ferroelectric to paraelectric phase transition in model ferroelectric materials such as $\mathrm{BaTi}{\mathrm{O}}_3$ is typically characterized by a sharp, well-defined dielectric constant peak at a specific transition temperature. However, under certain modifications of the parent material, this transition can become diffuse over a broad range of temperatures. This has garnered significant research attention over the past few decades, primarily because of its intriguing and not yet fully understood physical properties. The parameters developed to measure the diffuseness are also ambiguous. In this Letter, an investigation has been conducted to understand the transition dynamics of the nonrelaxor ferroelectric systems in the temperature interval over which the diffuse phase transition occurs. This is achieved by modeling the dielectric response phenomenologically, using a distribution of local transition temperatures. Moreover, a temperature-dependent differential analysis is introduced, enabling the clear demarcation of distinct dielectric regimes and providing enhanced insight into the evolution of the phase transition. It is strongly recommended that the degree of diffuseness γ parameter is uncertain in many senses. Hence, following the establishment, a simple yet effective measure of diffuseness is being proposed, offering a more accurate and physically meaningful estimation of the diffuse phase transition.

Driven systems offer the potential to realize a wide range of nonequilibrium phenomena that are inaccessible in static systems, such as discrete time crystals. Time rondeau crystals with a partial temporal order have been proposed as a distinctive prethermal phase of matter in systems driven by structured random protocols. Yet, heating is inevitable in closed systems and time rondeau crystals eventually melt. We introduce dissipation to counteract heating and demonstrate stable time rondeau crystals, which persist indefinitely, in a many-body interacting system. A key ingredient is synchronization in the noninteracting limit, which allows for stable time rondeau order without generating excessive heating. The presence of many-body interaction competes with synchronization and a desynchronization phase transition occurs at a finite interaction strength. This transition is well captured via a linear stability analysis of the underlying stochastic processes.