Using multiscale modeling we investigate layer-breathing phonons in ${MX}_2$ bilayers ($M=\text{Mo,}\text{W}$; $X=\text{S,}\text{Se}$) containing dislocations specific for lattice-relaxed moiré superlattices. The dislocations, forming in the bilayers with parallel and antiparallel alignment of layers, bring about spatial modulation of the interlayer distance, generating effective potentials that promote the emergence of one-dimensional quasibound bands of layer-breathing modes inside perfect dislocations. For parallel ${MX}_2$ bilayers, perfect dislocations host multiple quasibound bands, with frequencies above the layer-breathing mode in rhombohedral-stacked domains. In contrast, antiparallel bilayers exhibit only a single quasibound band arising for orientations close to the edge-dislocation type, having frequencies above the layer-breathing mode in 2H-stacked domains.

The classic Thouless-Kohmoto-Nightingale-Nijs theorem dictates that a single electron band of a lattice can only harbor an integer quantum Hall conductance as a multiple of $e^2/h$, while recent studies have pointed to the emergence of half-quantum anomalous Hall (HQAH) effect, though the underlying microscopic mechanisms remain controversial. Here we propose an ideal platform of $\mathrm{Mn}{\mathrm{Bi}}_2{\mathrm{Te}}_4/{\mathrm{Sb}}_2{\mathrm{Te}}_3$ that allows one to not only realize the HQAH effect at much higher temperatures, but also to critically assess the different contributions of the gapped and gapless Dirac bands. We first show that the top surface bands of the ${\mathrm{Sb}}_2{\mathrm{Te}}_3$ film become gapped, while the bottom surface bands remain gapless due to proximity coupling with the $\mathrm{Mn}{\mathrm{Bi}}_2{\mathrm{Te}}_4$ overlayer. Next we show that such a semimagnetic topological insulator harbors the HQAH effect at ∼20 K, with Cr doping enhancing it to as high as 67 K, driven by large magnetic anisotropy and strong magnetic coupling constants that raise the Curie temperature. Our detailed Berry curvature analysis further helps to reveal that, although the gapped surface bands can contribute to the Hall conductance when the chemical potential is tuned to overlap with the bands, these bands have no net contribution when the chemical potential is in the gapped region, leaving the gapless bands to be the sole contributor to the HQAH conductance. Counterintuitively, the part of the gapless bands within the gapped region of the top surface bands has no net contribution, thereby ensuring the plateau nature of the Hall conductance.

We show that a semi-Dirac (SD) system with an inversion symmetry breaking mass exhibits a topological phase transition when irradiated with off-resonant light. Using Floquet theory, we derive the band structure, Chern numbers, phase diagram, and we show that as the light intensity is swept at fixed mass, the SD system undergoes a normal-Chern-normal insulator transition. Along the phase boundaries, we observe single semi-Dirac-cone (SSDC) semimetal states in which one SD cone is gapless and the other is gapped. The nontrivial Berry curvature distribution $\mathrm{\Omega }\left(\mathbf{k}\right)\ne -\mathrm{\Omega }(-\mathbf{k})$ generates an orbital magnetization $M$ and anomalous Nernst (${\alpha }_{xy}$) and thermal Hall (${\kappa }_{xy}$) conductivities. We show that $M$ remains constant as the Fermi level $E_F$ scans the insulating gap, but it changes linearly with it in the Chern insulator (CI) phase, as expected. In the normal insulator phase, we find that ${\alpha }_{xy}$ exhibits a dip-peak profile that is reversed in the CI phase. We also find that switching the light's circular polarization from left to right induces a sign change in $M, {\alpha }_{xy}$, and ${\kappa }_{xy}$, regardless of the topological phase, thereby allowing us to reverse the direction of flow of the transverse charge and heat currents. Further, we evaluate the components of the charge (${\sigma }_{aa}$), thermoelectric (${\alpha }_{aa}$), and thermal (${\kappa }_{aa}$) conductivity tensors ($a=x,y$) and examine the effect of light on them. With a linear dispersion along the $y$-direction, we find that ${\alpha }_{yy}$ and ${\kappa }_{yy}$ are significantly larger than ${\alpha }_{xx}$ and ${\kappa }_{xx}$, respectively, due to the much larger squared Dirac velocity $v_y^2$ compared to $v_x^2$.

Spacetime supersymmetry (SUSY) that interchanges fermions and bosons is of great theoretical importance but has not yet been revealed experimentally in particle physics. It has also been desired to explore quantum-mechanical SUSY in microscopic lattice models. Inspired by the recent experiments of Floquet engineering of Rydberg atom arrays, we propose to simulate a quantum mechanical supersymmetric model and realize quantum mechanical SUSY in Floquet Rydberg atom arrays. Moreover, we utilize the supercharge dynamics to demonstrate the SUSY property of the model under investigation: the expectation value of supercharge freezes under time evolution for supersymmetric lattice models in contrast to the trivial oscillation for generic nonsupersymmetric lattice models. The proposal is validated on a direct simulation of Rydberg atom arrays' dynamics and is ready for experiments. This work sheds light on the future experimental exploration of SUSY with the help of Rydberg atom arrays.

Integrability is an exceptional property believed to hold only for systems with fine-tuned parameters. Contrary, we explicitly show that in homogeneous nearest-neighbor qubit circuits with a U(1) symmetry, i.e., circuits that repeatedly apply the same magnetization-conserving two-qubit gate, this is not the case. There, integrability is generic: All such brickwall qubit circuits are integrable, even with a randomly selected gate. We identify two phases with different conservation laws, transport properties, and strong zero edge modes. Experimentally important is the fact that varying any one of the parameters in the generic U(1) gate, one will typically cross the critical manifold that separates the two phases. Finally, we report on an unconventional time-reversal symmetry causing the system with open boundary conditions to be in the orthogonal class, while the one with periodic boundary conditions is in the unitary class.

We perform a fluctuation analysis of the pairing interaction in the hole-doped Hubbard model within the dynamical cluster approximation. Our analysis reveals that spin-fluctuation-mediated pairing differs qualitatively in the over- and underdoped regimes. In the underdoped regime, spin fluctuations open a pseudogap. We show that in this regime the spin-fermion coupling mediates a giant attraction between antinodal fermions. This explains why superconductivity survives at underdoping in the Hubbard model and cuprates, despite the lack of coherent fermionic quasiparticles in the pseudogap regime.

We show that the remarkably small Fermi-liquid coherence scale and large effective mass observed in ${\mathrm{LiV}}_2{\mathrm{O}}_4$ are due to the proximity of a Hund-assisted orbital-selective Mott phase (OSMP). Our work is based on an ab initio dynamical mean-field approach, combining several quantum impurity solvers to capture the physics from high to very low temperature. We find that the Hund coupling plays a crucial role in rearranging the orbital populations and in generating the heavy mass and low coherence scale. The latter is found to be approximately 1–2 Kelvin, even though the most correlated orbital is found to be significantly doped ($\sim 10\%$) away from half-filling. A flat quasiparticle band appears near the Fermi level as a result of the strong electronic correlations. Finally, we discuss our results in comparison to experiments.

Valence bond (VB) states as the formation mechanism of Cooper pairs, eventually leading to high-temperature superconductivity, remain a controversial topic. Although various VB-like states find variational relevance in the description of specific spin models and quantum spin liquids, in the realm of many-body fermionic Hamiltonians, the evidence for such states as ground-state wave functions remains elusive, challenging the valence-bond pairing mechanism. Here, we present evidence of a VB ground state with pairing tendencies, particularly at finite doping. We achieved this for the generic two-orbital Hubbard model in low dimension, where the VB states can be associated with the presence of the topological order manifested by edge states.

Recent experimental and theoretical works have revealed a strong analogy between (fractional) Chern insulators in multilayered moiré systems and (fractional) quantum Hall states, due to the emergence of a fictitious magnetic field in the former. We propose a simple interpretation of this magnetic field, attributing it to a real-space winding of the layer spinor in the electronic bands. Ideal Chern bands factorize into a lowest Landau level (LLL) and a spinor wave function. We generally demonstrate that the geometric phase arising from the skyrmionlike winding of the spinor compensates the LLL magnetic phase. The Skyrme texture persists in twisted bilayer graphene well beyond the chiral limit, under realistic corrugation condictions, making it an experimentally testable feature. We extend our findings for higher Chern numbers $\left|C\right|>1$, where we find $\left|C\right|$ color Landau levels carried by $\left|C\right|$ skyrmions. Their winding requires the number of layers $L$ to exceed the Chern number, $L\ge \left|C\right|+1$. Each skyrmion exhibits a Pontryagin winding index of $-1$. We verify our predictions at the first magic angle of twisted bilayer, trilayer, and monolayer-bilayer graphene.

Excitons in monolayer transition metal dichalcogenides (TMDs) dominate their optical response due to exceptionally large binding energies arising from their two-dimensional nature. Several theoretical models have been proposed to describe this excitonic behavior, however, it remains unclear which model most accurately captures the underlying physical properties of the response. In this Letter, we experimentally measure the optical response of different high-quality monolayer TMD heterostructures and compare the results to the different theoretical models to address this uncertainty. Our results univocally show that in high-quality TMD heterostructures, quantum mechanical interactions in the form of a quantum pure dephasing plays a dominant role compared to other physical constituents. This finding is especially significant owing to the inability of other approaches to experimentally isolate and measure the quantum pure dephasing contribution to the excitonic response. These findings establish a robust framework for understanding and predicting the optical properties of excitons in monolayer TMD-based heterostructures, which are important for both fundamental research and optoelectronic device applications.

We investigate the universal fluctuations of localized wave functions in the Fock space of two interacting particles in one-dimensional disordered systems, focusing on the interplay between random potentials and random long-range interactions. By mapping the system onto a directed polymer problem, we show that random potentials alone produce correlated energies for the sites in the Fock space, giving rise to the fluctuation growth exponent $1/2$. Introducing random long-range interactions alters these correlations and drives the system's fluctuations into the Kardar-Parisi-Zhang universality class in (1+1)D with the exponent $1/3$. To validate the universality of the observed fluctuation scaling, we study a complex directed polymer model with competing point and columnar disorder. Our results confirm that columnar disorder corresponds to on-site energies in the Fock space from the random potentials, while point disorder models the effects of random long-range interactions between the two particles. These findings provide new insights into the Fock-space perspective for examining disordered quantum many-body systems, and they emphasize the critical role of disorder structure in determining the universality class of fluctuations in localized quantum systems.

The interface-driven spin-orbit coupling (SOC) mechanism in the oxide-based two-dimensional electron gas (2DEG) system can be very crucial to tune the magnetization dynamics. We have deposited ${\mathrm{LaTiO}}_3\left(\mathrm{LTO}\right)$ layer with varying thickness $\delta$ at the interface of ${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_3$ $(15 \mathrm{nm})/{\mathrm{SrTiO}}_3\left(001\right)$ [LSMO (15 nm)/STO(001)] thin film heterostructures. Through systematic and comprehensive ferromagnetic resonance (FMR) measurements, we observed changes in the effective magnetization, Gilbert damping, and magnetic anisotropy of the ferromagnetic LSMO layer on the increasing thickness of the interfacial LTO layer. The introduction of LTO layer at the LSMO/STO interface gives rise to an increase in effective magnetic field and in-plane magnetic anisotropy. We argue this is due to the enhanced Rashba effect at the LTO/STO interface. Furthermore, the polar angle variation of the FMR linewidth reveals the effect of induced Rashba field and magnetic inhomogeneity on the local variation of $4\pi M_{\mathrm{eff}}$ at the interface. Our study reveals tunable magnetization dynamics of LSMO with Rashba SOC and 2DEG resulting from varying the thickness of the LTO layer. This can be very promising to unlock novel functionalities in advanced nanoscale electronics and spintronics applications.

We have grown single crystals of ${\mathrm{La}}_{}$-substituted M-type strontium hexaferrites ${\mathrm{Sr}}_{1-x}{\mathrm{La}}_x{\mathrm{Fe}}_{12}{\mathrm{O}}_{19}$ using the traveling solvent floating zone technique, and investigated their magnetic and electrical properties. Although the saturation moment at room temperature increases monotonically with ${\mathrm{La}}_{}$ concentration $x$, its value at $5\mathrm{K}$ remains nearly constant up to $x=0.6$ and then slightly increases for higher $x$, suggesting that the magnetic moments at the minority spin sites tilt at low temperatures. At $5\mathrm{K}$, the shape of the magnetization curve exhibits qualitative changes at $x=1/3$ and $2/3$, which implies the formation of a triangular lattice of ${\mathrm{Fe}}^{2+}$ on the $2a$ sites. Our analysis of the magnetization curves at $5\mathrm{K}$ indicates that anisotropic exchange interactions between ${\mathrm{Fe}}^{2+}$ at the $2a$ sites enhance the anisotropy field for $x>1/3$. Furthermore, the temperature dependence of electrical resistivity suggests that the conduction mechanism changes around $150\mathrm{K}$, with the effects of localized ${\mathrm{Fe}}^{2+}$ ions being substantially reduced above this temperature.

${\mathrm{Mn}}_3{\mathrm{Si}}_2{\mathrm{Te}}_6$ is a ferrimagnetic topological nodal-line semiconductor that exhibits unconventional colossal magnetoresistance behavior, with short-range spin fluctuations being potentially intimately linked to the emergent properties. Here we determine the short-range magnetic order and anisotropy through total neutron scattering and polarized neutron powder diffraction measurements on polycrystalline ${\mathrm{Mn}}_3{\mathrm{Si}}_2{\mathrm{Te}}_6$. Strong in-plane anisotropy is quantified on the Mn ions through extraction of the local site susceptibility tensor. The real-space local spin structure is determined through the application of magnetic pair distribution function analysis covering a wide temperature range. Short-range order over a locally frustrated trimer of three nearest neighbors is found to exist well above the long-range ferrimagnetic transition.

We present a novel and efficient real space, semiclassical model of electric polarization with general applicability to any system in which screening plays an important role. This model includes the effects of both atomic and bond polarizabilities, the latter originating from the modification of local bond charge transfer energies induced by polarizing charges. The nonlinear interference of multiple polarization clouds and the emergence of local field effects are highlighted as key phenomena highly influencing the short-range screening of the Coulomb interaction. As a representative system to showcase this model, the screened interaction between doped holes in the ${\mathrm{CuO}}_2$ planes of cuprate high-temperature superconductors is investigated. This leads to the emergence of striking direction-dependent short-range minima in their Coulomb repulsion, which can strongly reduce the need for retardation effects and allow for an enhancement of the attractive interaction resulting from the exchange of bosons between two electrons or holes. This, in turn, enhances $T_C$, shortens the Cooper pair coherence length and supports the materialization of the pseudogap phase anisotropy observed in many high-$T_C$ superconductors.

In this work, we study the influence of disorder on the electronic structure of YbSb—a rare-earth monopnictide featuring a simple rocksalt (B1) crystal structure and a well-defined Fermi-surface topology—by employing first-principles density-functional theory. We focus on chemical disorder introduced through Te and Al doping, selected based on their thermodynamic stability in alloyed configurations, to understand how such perturbations modify the electronic states of YbSb. Our results indicate that Te doping predominantly introduces electronlike states at the $X$ and $L$ points, while Al doping leads to a suppression of holelike states at Γ, effectively driving the system from a semimetallic state to one characterized by very narrow-gap behavior at Γ. This modulation of the Fermi surface, particularly the reduction of central hole pockets at Γ, plays a central role in altering interpocket scattering—a mechanism critical for tuning quantum transport properties, including superconductivity. This disorder-driven modulation of the Fermi surface, particularly the suppression of central hole pockets at Γ, controls interpocket scattering, which is essential for optimizing quantum transport properties, including superconductivity. Our results show that disorder can be effectively used for engineering band topology, thereby tuning quantum related response through a tailored electronic structure.

Understanding interlayer charge dynamics in van der Waals heterostructures is vital for advancing optoelectronic applications. The photogenerated carrier dynamics in two-dimensional $g\text{−}{\mathrm{C}}_3{\mathrm{N}}_4/\mathrm{MoS}{\mathrm{i}}_2{\mathrm{N}}_4$ are systematically explored via nonadiabatic molecular dynamics simulations and first‐principles calculations. It is found that the heterostructure exhibits a type‐II band alignment with a direct band gap of 1.88 eV with enhanced visible light absorption and high carrier mobility. Photoexcited electrons oscillate between layers with an insufficient transfer, and 69% of holes localize on $g\text{−}{\mathrm{C}}_3{\mathrm{N}}_4$ within 32 fs. Applying an external electric field of +0.1 V/Å significantly facilitates charge spatial separation; nearly 73% of electrons transfer to $\mathrm{MoS}{\mathrm{i}}_2{\mathrm{N}}_4$ layer within 223 fs and 96% of holes localize on $g\text{−}{\mathrm{C}}_3{\mathrm{N}}_4$ layer within 47 fs. This can be ascribed to the stronger electron‐phonon coupling, dominated by the excitation of the $A_2^{{}^{\prime }3}$ mode at 1034 $\mathrm{c}{\mathrm{m}}^{-1}$. Meanwhile, introducing the external electric field of +0.1 V/Å weakens nonadiabatic couplings and accelerates decoherence, thereby prolonging the electron‐hole recombination time to 28 ns. These findings highlight the role of an external electric field in optimizing interlayer charge dynamics of two‐dimensional heterostructures for high‐performance optoelectronics.

Thermal emission is naturally spatially incoherent and lacks directionality. Here, we demonstrate that by precisely controlling the spatial temperature distribution within a solid, directional thermal emission can be achieved across a broad spectral range. These anisothermal sources open different avenues for manipulating radiative heat flux at the microscale and hold promise for applications in thermal management and energy conversion, enabling more efficient and targeted thermal control.