The non-Hermitian skin effect, in which eigenstates of non-Hermitian Hamiltonians are localized at one boundary in the open boundary condition, has attracted great interest recently. In this paper, we investigate the skin effect in one-dimensional dissipative quantum many-body systems, which we call the Liouvillian skin effect (LSE). We rigorously identify the existence of the LSE for generalized boundary conditions by solving the Liouvillian superoperator of an exactly solvable model with the advantage of the Bethe ansatz. The LSE is sensitive to boundary conditions where the signature is reflected in eigenfunctions of the system. We confirm that the LSE is fragile to a tiny coflow boundary hopping with non-Hermitian current but can survive a counterflow boundary hopping in the thermodynamic limit. Our work provides a prototypical example of exactly solvable dissipative quantum many-body lattice systems exhibiting the LSE for generalized boundary conditions. It can be further extended to other integrable open quantum many-body models.

Quasi-one-dimensional (quasi-1D) monochalcogenide compounds exhibit a strong in-plane anisotropy in their electronic band structure, which originates from their low crystallographic symmetry and provides an ideal platform for exploring collective electron behavior in confined systems. Here, we provide direct experimental evidence of electronic flat band near the Fermi level in quasi-1D InTe, using a combination of angle-resolved photoemission spectroscopy (ARPES), and density-functional theory (DFT). This flattened band extends about 0.4 ${\AA }^{-1}$ one dimensionally in $k$-space area around the $M$ point according to ARPES and DFT. Using scanning tunneling microscopy, we found a modulation in the density of states along the $\mathrm{I}{\mathrm{n}}^{1+}$ atoms, with a wavelength of two times the lattice constants. This periodic modulation order could be results from a Peierls instability, in which a spatial lattice distortion opens an electronic gap at the Fermi energy. Such quasi-1D InTe crystals provide a platform for fundamental research and future applications which relies on collective electronic behavior of a quasi-1D semiconductor.

Chalcogenide perovskite materials have been shown to exhibit excellent properties for optoelectronics and photovoltaics. The research, however, has been focused on the II-IV-${\mathrm{S}}_3$ series of compounds. Here, by theoretical calculation, we predict that in the III-III-${\mathrm{S}}_3$ perovskites, there could exist a transition between the indirect and direct band gaps induced by the coupling strength of the $d$ orbitals between the A-site and B-site cations. We validate this prediction by synthesizing ${\mathrm{LaScS}}_3$ through solid state reaction from three elemental materials. Micro-Raman analysis combined with Raman tensor calculations are used to identify the perovskite phase of micrometer-size grains, from which photoluminescence can be observed. The emitted light peaks at about 519 nm (or 2.39 eV), which corresponds to the largest band gap among the sulfide perovskites. The discovery of light-emitting ${\mathrm{LaScS}}_3$ enriches the family of chalcogenide perovskites for optoelectronic applications.

Noble gas elements exhibit chemical reactivity under high pressure, forming novel compounds through reactions with other substances, which has become a recent focus in condensed matter physics research. By combining first-principles calculations with crystal structure prediction methods, we propose six unconventional Xe-K compounds under high pressure, namely ${\mathrm{Xe}}_4\mathrm{K}$, ${\mathrm{Xe}}_3\mathrm{K}$, ${\mathrm{Xe}}_3{\mathrm{K}}_2$, ${\mathrm{Xe}}_2\mathrm{K}$, XeK, and ${\mathrm{XeK}}_4$. In addition to previously proposed Xe-rich compounds, we introduce an unconventional K-rich compound, ${\mathrm{XeK}}_4$, which remains stable over a considerable pressure range from 49 to 104 GPa and a high-pressure phase of ${\mathrm{Xe}}_3\mathrm{K}$. Both ${\mathrm{XeK}}_4$ and ${\mathrm{Xe}}_3\mathrm{K}$ demonstrate metallic properties with a strong ionic Xe-K bond within their stable pressure range. Further ab initio molecular dynamics simulations indicate that ${\mathrm{XeK}}_4$ undergoes a solid-to-liquid transition with increasing temperature, while the other Xe-K compounds maintain solid-state characteristics. The solid or liquid stability pressure ranges of Xe-K compounds cover the pressure and temperature conditions of the Earth's mantle, suggesting that ${\mathrm{XeK}}_4$ and other Xe-K compounds might act as possible constitutes and exist in the Earth's mantle. These results could provide essential information for understanding the Xe-K compounds and the Xe chemistry at high pressure.

The discovery of superconductivity at 80 K under high pressure in ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ presents the groundbreaking confirmation that high-$T_c$ superconductivity is a property of strongly correlated materials beyond cuprates. We use density functional theory calculations of the band structure of ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ under pressure to verify that the low-energy bands are composed almost exclusively of Ni $3d_{x^2-y^2}$ and O $2p$ orbitals. We deduce that the Ni $3d_{z^2}$ orbitals are essentially decoupled by the geometry of the high-pressure structure and by the effect of the Ni Hund coupling being strongly suppressed, which results from the enhanced interlayer antiferromagnetic interaction between $3d_{z^2}$ orbitals and the strong intralayer hybridization of the $3d_{x^2-y^2}$ orbitals with O $2p$. By introducing a tight-binding model for the Fermi surfaces and low-energy dispersions, we arrive at a bilayer $t\text{−}{t}_{\perp }\text{−}J$ model with strong interlayer hopping, which we show is a framework unifying ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ with cuprate materials possessing similar band structures, particularly the compounds ${\mathrm{La}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_6$, ${\mathrm{Pb}}_2{\mathrm{Sr}}_2{\mathrm{YCu}}_3{\mathrm{O}}_8$, and ${\mathrm{EuSr}}_2{\mathrm{Cu}}_2{\mathrm{NbO}}_8$. We use a renormalized mean-field theory to show that these systems should have $(d+is)$-wave superconductivity, with a dominant $d$-wave component and the high $T_c$ driven by the near-optimally doped $\beta$ band, while the $\alpha$ band adds an $s$-wave component that should lead to clear experimental signatures.

Hall viscosity is a nondissipative viscosity occurring in systems with broken time-reversal symmetry, such as quantum Hall phases and $p+ip$ superfluids. Despite Hall viscosity's expected ubiquity and past observations in: classical soft matter, optical, and graphene systems, it has yet to be measured experimentally in any macroscopic quantum state of matter. Toward this end, we describe the observable effects of Hall viscosity in a simple family of rotating Bose-Einstein condensates of electrically neutral bosons, in which all of the bosons condense into a single lowest Landau level (LLL) orbital. Such phases are accessible to current cold atom experiments, and we dub them LLL superfluids. We demonstrate that LLL superfluids possess a nonuniversal Hall viscosity, leading to a range of observable consequences such as rotation of vortex-antivortex dipoles and wave-vector-dependent corrections to the speed of sound. Furthermore, using a coherent state path integral approach, we present a microscopic derivation of the Landau-Ginzburg equations of a LLL superfluid, showing explicitly how Hall viscosity enters.

The quest to manipulate and understand superconductivity demands exploring diverse materials and unconventional behaviors. Here, we investigate the Berezinskii-Kosterlitz-Thouless (BKT) transition in ${\mathrm{ReN}}_x$ thin films, demonstrating their emergence as a compelling platform for studying this pivotal phenomenon. By systematically varying synthesis parameters, we achieve ${\mathrm{ReN}}_x$ films exhibiting a BKT transition comparable to what is known from ${\mathrm{NbN}}_x$ meander structure films. Detailed current-voltage measurements unlock the intrinsic parameters of the BKT transition, revealing the critical role of suppressed superconducting volume in pushing ${\mathrm{ReN}}_x$ towards the two-dimensional limit. Utilizing this two-dimensional electron system, we employ Beasley-Mooij-Orlando theory to extract the vortex unbinding transition temperature and superelectron density at the critical point. Further confirmation of the BKT transition is obtained through temperature-dependent resistivity, current-voltage, and magnetoresistance measurements. Our findings suggest that native disorder and inhomogeneity within ${\mathrm{ReN}}_x$ thin films act to suppress long-range coherence, ultimately driving the system towards the BKT regime. This work establishes ${\mathrm{ReN}}_x$ as a promising material for exploring BKT physics and paves the way for tailoring its properties for potential applications in superconducting devices.

Analytic continuation is a central step in the simulation of finite-temperature field theories in which numerically obtained Matsubara data are continued to the real frequency axis for a physical interpretation. Numerical analytic continuation is considered to be an ill-posed problem where uncertainties on the Matsubara axis are amplified exponentially. Here, we present a systematic and controlled procedure that approximates any Matsubara function by a minimal pole representation to within a predefined precision. We then show a systematic convergence to the exact spectral function on the real axis as a function of our control parameter for a range of physically relevant setups. Our methodology is robust to noise and paves the way towards reliable analytic continuation in many-body theory and, by providing access to the analytic structure of the functions, a direct theoretical interpretation of physical properties.

We present a general approach for detecting when a fusion category symmetry is anomalous, based on the existence of a special kind of Lagrangian algebra of the corresponding Drinfeld center. The Drinfeld center of a fusion category $\mathcal{A}$ describes a $(2+1)$-dimensional topological order whose gapped boundaries enumerate all $(1+1)$-dimensional gapped phases with the fusion category symmetry, which may be spontaneously broken. There always exists a gapped boundary, given by the electric Lagrangian algebra, that describes a phase with $\mathcal{A}$ fully spontaneously broken. The symmetry defects of this boundary can be identified with the objects in $\mathcal{A}$. We observe that if there exists a different gapped boundary, given by a magnetic Lagrangian algebra, then there exists a gapped phase where $\mathcal{A}$ is not spontaneously broken at all, which means that $\mathcal{A}$ is not anomalous. In certain cases, we show that requiring the existence of such a magnetic Lagrangian algebra leads to highly computable obstructions to $\mathcal{A}$ being anomaly free. As an application, we consider the Drinfeld centers of ${\mathbb{Z}}_N\times {\mathbb{Z}}_N$ Tambara-Yamagami fusion categories and recover known results from the study of fiber functors.

Dopants can bring new functionalities to semiconductor materials; therefore, it is desirable to optimize the properties of dopants to achieve better performance. In this work, we demonstrate that the property of a dopant can be tuned to various extents by the polarization effect. We have proposed a mix-phase AlN/ScN superlattice system as substrate, whose built-in polarization is an order of magnitude larger than that in a AlN/GaN superlattice. Taking the $3d$ transition metal as a dopant, we show by first-principles calculations that the stable electronic configuration of individual dopants and the spin-exchange interaction between different dopants can be effectively controlled by the polarization effect. Specifically, for the case of ${\mathrm{Co}}_{\mathrm{Sc}}$, the relative stability between the 0 ${\mu }_B$ ($t_{2g}^6{e}_g^0$) and the 4 ${\mu }_B$ ($t_{2g}^4{e}_g^2$) magnetic states can be tuned by varying the doping positions along the polarization direction. For the case of ${\mathrm{V}}_{\mathrm{Al}}$ with $e^2{t}_2^0$ electronic configuration, the ferromagnetic interaction between half-filled $e$ states and empty $t_2$ states can be enhanced when the adjacent ${\mathrm{V}}_{\mathrm{Al}}$ dopants are at inequivalent doping positions along the polarization direction. These results show that the polarization effect has a significant impact on dopant properties in semiconductors. Further, as the AlN/ScN material system is compatible with existing complementary metal-oxide-semiconductor (CMOS) back-end processes, it can serve as a versatile platform to obtain large polarization fields and thus can achieve effective polarization control of dopant properties experimentally.

Orbitronics harnesses nonequilibrium densities and flows of electrons' orbital angular momentum (OAM). Although the OAM must be long lived to be useful in information processing, the mechanisms leading to OAM nonconservation remain unknown. Here we show that an electric field induces an intrinsic torque on the OAM mediated by the quantum metric tensor, without spin-orbit coupling or magnetic fields. The torque vanishes in pseudospin-1/2 systems with particle-hole symmetry but is nonzero in the presence of nontrivial textures. We discuss implications for topological materials and strategies for experimental observation.

The emergence of effective $S=1/2$ spins at the edges of $S=1$ Haldane spin chains is one of the simplest examples of fractionalization. Whereas there is indirect evidence of this phenomenon, direct measurement of the magnetic moment of an individual edge spin remains to be done. Here we show how scanning tunnel microscopy electron-spin resonance (ESR-STM) can be used to map the stray field created by the fractional $S=1/2$ edge spin and we propose efficient methods to invert the Biot-Savart equation, obtaining the edge magnetization map. This permits one to determine unambiguously the two outstanding emergent properties of fractional degrees of freedom, namely, their fractional magnetic moment and their localization length $\xi$.

The notion of the flow introduced by Kitaev is a manifestly topological formulation of the winding number on a real lattice. First, we show in this paper that the flow is quite useful for practical numerical computations for systems without translational invariance. Second, we extend it to three dimensions. Namely, we derive a formula of the flow on a three-dimensional lattice, which corresponds to the conventional winding number when systems have translational invariance.

A quantum mechanical theory for description of electronic quasistationary states in two-dimensional (2D) layered semiconductor nanostructure was developed. A constant external magnetic field $B$ was directed along semiconductor layers. The presence of internal electric fields $F$ originated from the potential barriers and wells in semiconductor layers was taken into account. The vector of $F$ was directed perpendicularly to semiconductor layers. The interaction of tunneled electrons with a time-dependent electromagnetic fields was analyzed in detail. An approach to obtain an exact solution to the problem based on a combination of the Lewis-Riesenfeld method for complete Schrödinger equation and scattering theory was developed. Application of the scattering theory in combination with the S-matrix and transfer-matrix methods allowed us to calculate the electron quasistationary spectra. Effects of magnetic field on the resonant energy and width of electronic quasistationary states as well as on the electronic conductivity were also discussed.

We investigate the nonlinear magneto-optical response in noncentrosymmetric magnetic Weyl semimetals featuring a quadratic tilt, focusing particularly on the influence of the van Hove singularity (VHS). In the absence of a magnetic field, the second-order nonlinear Drude conductivity components exhibit inflection or dip behavior across the VHS. In contrast, the second-order nonlinear anomalous Hall conductivity, primarily governed by the Berry curvature dipole, manifests a subtle plateaulike structure. As the tilt strength increases, the VHS energy rises, thereby amplifying the VHS-induced characteristics within these second-order conductivity components. However, we show that in the presence of a magnetic field, the resultant magnetic moment suppresses nonlinear electron transport while enhancing nonlinear hole transport. This effect serves to mitigate the impact of the VHS, resulting specifically in an asymmetric peak or a kinklike structure in the magnetic-field-induced contribution to the second-order nonlinear conductivity near the Weyl nodes. These findings provide insights into the intricate interplay among the VHS, Berry curvature, and magnetic moment in nonlinear magneto-optical transport through noncentrosymmetric magnetic Weyl semimetals.

We study measurement-induced entanglement and control phase transitions in a quantum and stochastic analog of the Bernoulli map subjected to a classically inspired control protocol. When entangling gates are restricted to the Clifford group, separate entanglement ($p_{\mathrm{ent}}$) and control ($p_{\mathrm{ctrl}}$) transitions emerge, revealing two distinct universality classes. The control transition has critical exponents $\nu$ and $z$ consistent with the classical map (a random walk) while the entanglement transition is revealed to have similar exponents as the measurement-induced phase transition in Clifford hybrid dynamics. This is distinct from the case of generic entangling gates with nonlocal control in the same model, where $p_{\mathrm{ent}}=p_{\mathrm{ctrl}}$ and universality is controlled by the random walk.

We revisit the magnetic properties of the hexagonal ferrite ${\mathrm{PbFe}}_{12-x}{\mathrm{Ga}}_x{\mathrm{O}}_{19}$. Recent experiments have reported puzzling dependences of the ordering temperature and the saturation magnetization on the Ga concentration $x$. To explain these observations, we perform large-scale Monte Carlo simulations, focusing on the effects of an unequal distribution of the Ga impurities over the five distinct Fe sublattices. Ab initio density-functional calculations predict that the Ga ions preferably occupy the $12k$ sublattice and (to a lesser extent) the $2a$ sublattice. We incorporate this insight into a nonuniform model of the Ga distribution. Monte Carlo simulations using this model lead to an excellent agreement between the theoretical and experimental values of the ordering temperature and saturation magnetization, indicating that the unequal distribution of the Ga impurities is the main reason for the unusual magnetic properties of ${\mathrm{PbFe}}_{12-x}{\mathrm{Ga}}_x{\mathrm{O}}_{19}$. We also compute the temperature and concentration dependences of the sublattice magnetizations, and we study the character of the zero-temperature transition that takes place when the ordering temperature is tuned to zero.

We present a theory of the realization of a ferromagnetic Haldane state in a spin-2 bilinear-biquadratic spin system on an orthogonal-dimer chain. The coexistence of a ferromagnetic state and a Haldane state is due to the rigorous correspondence between the eigenstates of a spin-2 model and a spin-$\frac{1}{2}$ Heisenberg model, i.e., “eigensystem embedding.” Numerical exact-diagonalization calculations indicate that the ground state in the model is a fractionally magnetized $M=3/4$ Haldane state. Moreover, a ferromagnetic-dimer multiplet state is an exact ground state on a lattice, where the direct product of dimer singlet states is the ground state in a spin-$\frac{1}{2}$ Heisenberg model that includes one-, two-, and three-dimensional orthogonal-dimer lattices. Eigensystem embedding demonstrates that a quantum ferromagnet can be obtained for an arbitrary spin $S\geqq 2$ in any dimension and for any lattice in which anomalous ground states are realized in a spin-$\frac{1}{2}$ Heisenberg model.