While the stripe phase has been observed not only in monolayer cuprates but also in bilayer cuprates, research on its behavior in bilayer cuprates has been limited. Using constrained path quantum Monte Carlo, we explore the effect of stripes on the bilayer square lattice. We find the system exhibits short-range antiferromagnetism, which is enhanced by stripes and is strongest when the electron density of the interstriped rows reaches half-filling. The hole doping concentration plays a crucial role in the interaction between stripes and superconductivity. The $d$-wave pairing is enhanced by stripe potential $V_0$ at the hole doping ${\delta }_h=1/4$, whereas it is suppressed by stripe potential $V_0$ at the hole doping ${\delta }_h=1/8$. We elucidate this phenomenon through an analysis of the magnetism of the interstriped rows. Furthermore, the effective $d$-wave pairing is stronger in the bilayer model compared to the monolayer model when stripes are introduced on the square lattice. Overall, our unbiased numerical simulations provide a further understanding of the crossed bilayer square lattice model.

It is quite intriguing to investigate the transition from a topological insulator (TI) phase to a topological crystalline insulator (TCI) phase in a material, as the latter has an advantage over the former in controlled device applications. This work investigates the existence of this dual topological behavior in the family of Sn-based ternary chalcogenides $\mathrm{PbSn}{X}_2$ ($X$ = S, Se, Te) under hydrostatic pressure using a first-principles approach. These materials are dynamically stable at ambient and elevated pressure conditions, up to which the topological phase transitions (TPTs) are studied. This family has a topologically trivial ground state with direct band gap values 0.338, 0.183, and 0.217 eV for ${\mathrm{PbSnS}}_2, {\mathrm{PbSnSe}}_2$, and ${\mathrm{PbSnTe}}_2$, respectively. The first TPT, i.e., the TI phase, for these materials is observed under the effect of external pressures of 5, 2.5, and 3.5 GPa, with a single band inversion at the $F$ point in the bulk band structure and an odd number of Dirac cones along the (111) surface. A further increase in pressures to 5.5, 3, and 4 GPa results in another band inversion at the $\mathrm{\Gamma }$ point and an even number of Dirac cones along the (111) plane. The even number of band inversions suggest that the ($\overline{1}2\overline{1}$) surface has mirror symmetry around the ($10\overline{1}$) plane, which confirms the existence of the TCI phase. This TCI phase is further corroborated by the even value of the mirror Chern number calculated using the winding of Wannier charge centers.

The enhancement of thermoelectric conversion efficiency is exciting but quite challenging due to the conflicting relationships among the key parameters for the thermoelectric performance. Herein, we comprehensively investigate the thermoelectric properties of the novel $X\mathrm{AgTe}$ ($X=\mathrm{K}$, Rb, Cs) materials using advanced first-principles calculations. These materials exhibit favorable stability and relatively low formation energies, making them amenable to preparation under conventional conditions. Their unique hierarchical bonding configuration and the rattling vibration modes of Ag induce the strong high-order phonon anharmonicity. On the other hand, their distinctive electronic structure with the coexistence of high-dispersion valleys and flat band edges leads to a high power factor. As a result, the proposed $X\mathrm{AgTe}$ series possesses both inferior thermal transport and superior electronic transport properties, consequently yielding the outstanding thermoelectric performance. Finally, the impressive peak thermoelectric figure of merit, $ZT>3$, for $p$-type doping, and $ZT>2$ for $n$-type doping were obtained. This study elucidates the underlying physical mechanism for the exceptional thermoelectric performance of $X\mathrm{AgTe}$ and opens pathways for the practical applications of thermoelectric materials.

Non-Hermitian systems exhibit two distinct topological classifications based on their gap structure: line-gap and point-gap topologies. Although point-gap topology is intrinsic to non-Hermitian systems, the systematic construction of the point-gapped topological phases remains challenging. Here, we present the Floquet engineering approach for realizing point-gapped topological superconductors. By combining Floquet theory with particle-hole symmetry, we show that a point gap hosting robust Majorana edge modes emerges at the overlap of Floquet bands with opposite winding numbers. In the thermodynamic limit, even weak non-Hermiticity opens a point gap from a gapless spectrum, driving a topological phase transition and breaking non-Bloch parity-time ($\mathcal{PT}$) symmetry. This transition is accompanied by the appearance of the Floquet $Z_2$ skin effect. Furthermore, the point-gapped topological phase and the non-Bloch $\mathcal{PT}$ symmetry exhibit size-dependent phenomena driven by the critical skin effect. Our work offers a pathway for exploring the point-gapped topological phases in non-Hermitian systems.

Thermal Hall transport has emerged as a valuable tool for probing the fractionalized excitations in chiral quantum spin liquids. Observing quantized thermal Hall response, expected at temperatures below the spectral gap, has been challenging and controversial. The finite-temperature behavior, especially in the quantum critical regime above the spectral gap, can provide useful signatures of the underlying topological order. In this context, we study the spin-$1/2$ Heisenberg antiferromagnet on a kagome lattice that is believed to be a $\mathrm{U}\left(1\right)$ Dirac spin liquid over a wide intermediate energy range. Scalar spin chirality perturbations turn this into a gapped Abelian chiral spin liquid with semionic topological order. Using a recently developed large-$N$ technique [Guo et al., Phys. Rev. B 101, 195126 (2020)], we obtain explicit expressions for the thermal Hall conductivity ${\kappa }_{xy}$ at finite temperatures, taking into account both matter and gauge fluctuations. At low temperatures below the spectral gap, the quantized thermal Hall response agrees with that expected from conformal field theory and gravitational anomaly arguments. Our main finding is that in a large temperature window spanning the spectral gap and the Curie temperature scales where quantum critical fluctuations dominate, ${\kappa }_{xy}/T$ obeys a power law with logarithmic corrections. Our analysis also provides a route to understanding the thermal Hall response at higher temperatures in the quantum critical regime.

The geometric frustration of kagome metals leads to flat bands, resulting in rich correlated states. However, there is a deeper question regarding the formation of flat bands, i.e., whether the flat-band-induced strong correlations would in turn stabilize the kagome lattice and further reinforce the flat bands. Recently, flat bands and Kondo-like physics are observed in a bilayer kagome metal ${\mathrm{CsCr}}_6{\mathrm{Sb}}_6$. The inter-kagome-layer coupling provides another degree of freedom to explore such physics. Here, based on density functional theory plus dynamical mean-field theory (DFT+DMFT) calculations, we show extremely flat bands in ${\mathrm{CsCr}}_6{\mathrm{Sb}}_6$, consistent with experiment. As temperature decreases, it undergoes an incoherence-to-coherence crossover and shows a resonance peak near the Fermi level. Surprisingly, we find that the inter-kagome-layer distance will collapse by about 20% if ignoring the strong electron correlation in DFT calculations, which will destroy the flat bands near the Fermi level due to a significant enhancement of the interlayer orbital hybridization. In contrast, it will not collapse after capturing the strong correlations in DFT+DMFT calculations. We thus reveal a positive feedback effect in the kagome metal that flat bands would reinforce themselves by stabilizing the lattice via the strong correlations they induced. This goes beyond our common understanding that the kagome lattice directly leads to flat bands because of the destructive interference of electron hopping, but ignoring the strong positive feedback effect between the electron correlations and kagome lattice.

The chiral-induced spin selectivity (CISS) effect, a phenomenon where the chirality of molecules imparts significant spin selectivity to electron transfer processes, has garnered increasing interest among the chemistry, biology, and physics communities. Although this effect was discovered more than a decade ago, the dynamical process of how electron spin polarization is caused by chiral molecules is still unclear. Here, we propose a dynamical theory of electron transfer in donor-chiral molecule bridge-acceptor systems without electrodes or substrates based on the Lindblad-type master equation. We demonstrate that the molecular spin-orbit coupling generates unequal spin velocities and achieves steady spin polarization with the help of dephasing. Our work elucidates the dynamical process of CISS and may promote the applications of chiral-based spintronic devices.

In contrast to the conventional (first-order) non-Hermitian skin effect (NHSE) in a $d$-dimensional system with linear size $L$, the $n\mathrm{th}$-order (higher-order) NHSE is characterized by skin modes localized at lower-dimensional boundaries of dimension $(d-n)$. The total number of these modes scales linearly with the system size $L$. Significant progress has been made in understanding higher-order NHSE in noninteracting systems. In this work, we demonstrate the many-body interaction-induced second-order skin effect in a two-dimensional non-Hermitian bosonic system. Specifically, we construct a square lattice that incorporates nonreciprocal single-boson hopping, on-site many-body interactions, and two-boson pairing hopping. In the absence of interactions, no second-order NHSE is observed. However, with the inclusion of interactions, we identify interaction-induced skin modes for in-gap doublon states (i.e., bound pairs of bosons) localized at the corners of the lattice, while the bulk doublon states remain extended. These corner-localized skin modes arise from the interplay between interaction-induced edge states, localized along one-dimensional boundaries, and the nonreciprocal hopping along these boundaries. Furthermore, the number of corner skin modes scales linearly with the system size, confirming the presence of second-order NHSE in this interacting system. Our findings introduce an approach to realizing higher-order skin effects by leveraging interactions.

Surface-plasmon polaritons (SPPs) are electromagnetic waves that propagate along metal-dielectric interfaces, with important applications in sensing, energy, and nanotechnology. While the behavior of SPPs in single metal slabs is well understood, the coupling between plasmon modes in multilayer systems has received less attention. In this paper, we explore the response functions of SPPs in single-slab, double-slab, and two-different-slab systems using the jellium model. Thanks to a comparison with classical models, in this paper, we reveal how quantum effects influence the resonance frequencies of these modes. We also detail the spatial description of the different SPP modes and unveil how their coupling occurs in two-different-slab systems. These findings provide insights into the behavior of SPPs, especially in complex nanostructures.

We investigate a hybrid thermal machine based on a single closed quantum Hall edge channel forming a quantum dot. It is tunneling coupled with two quantum Hall states at $\nu =2$ in contact with reservoirs at different temperatures and chemical potentials. One of these edge states is also driven out of equilibrium by means of a periodic train of Lorentzian voltage pulses. This device allows to explore various possible working regimes including the engine, the heat pump, and the refrigerator configuration. Regions where two regimes coexist can also be identified. Moreover, the proposed setup exhibits robustness and in some parameter regions also slightly enhanced performance in the presence of electron-electron interactions.

We examine the onset of Anderson localization in three-dimensional systems with structural disorder in form of lattice irregularities and in the absence of any on-site disordered potential. Analyzing two models with distinct types of lattice regularities, we show that the Anderson localization transition occurs when the strength of the structural disorder is smoothly increased. Performing finite-size scaling analysis, we show that the transition belongs to the same universality class as regular Anderson localization induced by on-site disorder. Our paper identifies a class of structurally disordered lattice models in which destructive interference of matter waves may inhibit transport and lead to a transition between metallic and localized phases.

Focusing on the recently discussed two-dimensional (2D) ferromagnetic compound, CrSBr, with a larger than 100 K transition temperature, we analyze its unusual electronic structure using a combination of numerical techniques. Our findings indicate magnetism to be driven by a two-sublattice double exchange mechanism. Our results reproduce the large magnetic transition temperature of CrSBr, as well as the significantly suppressed transition temperature in the related compound, ${\mathrm{CrPS}}_4$. The same mechanism rationalizes the observed negative, hysteretic magnetoresistance in bilayer CrSBr. Based on the discussed mechanism, we predict that the magnetic transition temperature may be further increased for the 2D semiconducting magnet CrSeBr and 2D metallic magnet CrTeBr.

The triangular-lattice quantum Ising antiferromagnet is a promising platform for realizing Anderson's quantum spin liquid, though finding suitable materials to realize it remains a challenge. Here, we present a comprehensive study of ${\mathrm{NaTmSe}}_2$ using magnetization, specific heat, neutron scattering, and muon spin relaxation, combined with theoretical calculations. We demonstrate that ${\mathrm{NaTmSe}}_2$ realizes the transverse field Ising model and quantitatively determine its exchange parameters. Our results reveal a multipolar spin-polarized state coexisting with a dipolar spin-disordered state. These states feature gapless spinon excitations mediated by the multipolar moments. The study shows how multiple types of magnetism can emerge in distinct magnetic channels (dipolar and multipolar) within a single magnet, advancing our understanding of spin-frustrated Ising physics and opening pathways for different quantum computing applications.

The nonuniform distribution of metal-oxygen bonding, indicative of distortion of corner-sharing octahedra, at the interfaces of isovalent perovskite transition-metal oxide heterostructures has been shown to be an excellent way to tailor their electronic and magnetic properties. Here, we demonstrate that the nonuniform distribution of metal-oxygen bonding at the interfaces of isovalent $\mathrm{L}{\mathrm{a}}_{0.67}\mathrm{S}{\mathrm{r}}_{0.33}\mathrm{Mn}{\mathrm{O}}_3/\mathrm{L}{\mathrm{a}}_{0.67}\mathrm{C}{\mathrm{a}}_{0.33}\mathrm{Mn}{\mathrm{O}}_3$ heterostructures modify the phase coexistence in this weakly phase-separated system. Combining depth-dependent magnetic characterization using polarized neutron reflectivity, x-ray scattering, and macroscopic magnetization measurements, we report on interface-driven asymmetric magnetization and magnetic phase separation as a function of depth, suggesting different ordering temperatures for different regions (interface and bulk) of the film. The results also predict a low-temperature exchange bias for these all-ferromagnetic-based heterostructures. In this paper, we provide an experimental investigation of interface-driven magnetism and magnetic phase separation in complex oxide heterostructures.

The ferrimagnetic nodal-line semiconductor ${\mathrm{Mn}}_3{\mathrm{Si}}_2{\mathrm{Te}}_6$ exhibits colossal magnetoresistance (CMR) owing to chiral orbital currents (COC). COC are developed because of spin-orbit interaction (SOI) associated with the tellurium (Te) atoms. Here, we observe that upon chemical substitution of Te atoms with selenium (Se), the COC, which run along the Te-Te edges of the ${\mathrm{MnTe}}_6$ octahedra, become weaker and thus affects the angular magnetoresistance (MR) of ${\mathrm{Mn}}_3{\mathrm{Si}}_2{\mathrm{Te}}_6$. We find that the application of magnetic field along the easy axis leads to a considerable drop in resistance in substituted crystals, which otherwise exhibit weak MR. On the other hand, the CMR effect along the partially polarized magnetization direction is found to be only marginally affected by the substitution and persists even at a significantly high concentration of Se.

Combining transport and magnetization measurements, we discover the emergence of a tricritical point connecting the antiferromagnetic, metamagnetic, and paramagnetic regions in ${\mathrm{MnBi}}_2{\mathrm{Te}}_4$, a magnetic topological insulator candidate which can potentially exhibit axion electrodynamics. We observe a unique magnetic field-driven phase diagram where the second-order antiferromagnetic to paramagnetic phase boundary bifurcates into two first-order lines at the tricritical point. The two first-order lines enclosing the metamagnetic phase eventually terminate at the quantum critical endpoints with the application of magnetic field.

The compound ${\mathrm{GdRh}}_2{\mathrm{Si}}_2$ crystallizes in the body-centered-tetragonal ${\mathrm{ThCr}}_2{\mathrm{Si}}_2$ structure and exhibits $A$-type antiferromagnetic order below its Néel temperature $T_{\mathrm{N}}=107$ K where the Gd moments are ferromagnetically aligned in the $ab$ plane with the moments in adjacent planes aligned antiferromagnetically. Previously, the nonlinear low-field magnetization versus field $M_{ab}(H\parallel [1,0,0])$ measurements on single crystals were interpreted in terms of a mean-field model. Here, we reinterpret this nonlinearity more simply in terms of the response of the ordered moments in four noninteracting tetragonal domains to the applied field and find good agreement with our theory.

We report the hydrostatic pressure effect on multiple magnetic states of noncentrosymmetric semimetal NdAlSi through electrical transport in a cubic anvil pressure cell up to 12.0 GPa. NdAlSi undergoes two successive magnetic transitions, an antiferromagnetic [AFM(I)] order at $T_{\mathrm{m}1}\sim 7.2\mathrm{K}$ and a ferrimagnetic (FIM) state at $T_{\mathrm{m}2}\sim 3.3\mathrm{K}$ at ambient pressure. Both are found to enhance initially with a positive pressure coefficient of $d{T}_{\mathrm{AFM}\left(\mathrm{I}\right)}/dP\approx 0.092$ and $d{T}_{\mathrm{FIM}}/dP\approx 0.55\mathrm{K}/\mathrm{GPa}$, respectively, and overlap at a critical pressure of $\sim 8.5\mathrm{GPa}$. With further increasing pressures, they are completely replaced by another antiferromagnetic [AFM(II)] state, which increases with $d{T}_{\mathrm{AFM}\left(\mathrm{II}\right)}/dP\approx 0.80\mathrm{K}/\mathrm{GPa}$. At the same time, the critical field for the FIM and/or AFM(II) to a full polarized paramagnetic (PM) phase transition sharply decreases by nearly one order of magnitude. A comprehensive temperature-pressure phase diagram manifests a tetracritical point for FIM, AFM(I), AFM(II), and PM states coinciding at 8.5 GPa and 8.0 K, as the indication for strong competitions of multiple magnetic states. The analysis of Hall conductivity reveals that carrier concentration and electron mobility strongly depend on magnetic ground states and physical pressure, and the FIM-AFM(II) and AFM(II)-PM transitions accompanying a pressure-induced Fermi-surface reconstruction. Our study provides an excellent example of regulating Weyl-mediated magnetism via a clean physical pressure route.