Recent experiments have reported that novel physics emerge in open quantum many-body systems due to an interplay of interactions and dissipation, which stimulate theoretical studies of the many-body Lindblad equation. Although the strong dissipation regime receives considerable interest in this context, this work focuses on the weak bulk dissipation. By examining the spectral property of the many-body Lindblad generator for specific models, we find that its spectral gap shows singularity in the weak dissipation limit when the thermodynamic limit is taken first. Based on analytical arguments and numerical calculations, we conjecture that such a singularity is generic in bulk-dissipated quantum many-body systems and is related to the concept of the Ruelle-Pollicott resonance in chaos theory, which determines the timescale of thermalization of an isolated system. This conjecture suggests that the many-body Lindblad equation in the weak dissipation regime contains nontrivial information on intrinsic properties of a quantum many-body system.

Kagome metals with charge density wave (CDW) order exhibit a broad spectrum of intriguing quantum phenomena. The recent discovery of the novel kagome CDW compound ${\mathrm{ScV}}_6{\mathrm{Sn}}_6$ has spurred significant interest. However, understanding the interplay between CDW and the bulk electronic structure has been obscured by a profusion of surface states and terminations in this quantum material. Here, we employ photoemission spectroscopy and potassium dosing to elucidate the complete bulk band structure of ${\mathrm{ScV}}_6{\mathrm{Sn}}_6$, revealing multiple van Hove singularities near the Fermi level. We surprisingly discover a robust spin-polarized topological Dirac surface resonance state at the $M$ point within the twofold van Hove singularities. Assisted by first-principles calculations, the temperature dependence of the $k_z$-resolved angle-resolved photoemission spectroscopy spectrum provides unequivocal evidence for the proposed $\sqrt{3}\times \sqrt{3}\times 3$ charge order over other candidates. Our work not only enhances the understanding of the CDW-dependent bulk and surface states in ${\mathrm{ScV}}_6{\mathrm{Sn}}_6$, but also establishes an essential foundation for potential manipulation of the CDW order in kagome materials.

We reveal the connection between two-dimensional subsystem symmetry-protected topological (SSPT) states and two-dimensional topological orders via a self-dual frustrated toric code model. This model, an enrichment of the toric code (TC) with its dual interactions, can be mapped to a model defined on the dual lattice with subsystem symmetries and subextensive ground state degeneracy. The map connects exactly the frustrated TC to two copies of the topological plaquette Ising model (TPIM), as a strong SSPT model with linear subsystem symmetries. The membrane order parameter of the TPIM is exactly mapped to dual TC stabilizers as the order parameter of the frustrated TC model, SSPT gapless edge states of the TPIM are mapped to zero-energy dangling operators under open boundaries, and the transition from the SSPT-ordered TPIM to the trivial paramagnetic phase is mapped to the transition between two distinct topological orders. We also demonstrate that this mapping can be used to elucidate the structure of other SSPT models, reflecting the subtle linkage between SSPT order and topological order in two dimensions.

Quantum simulators offer powerful means to investigate strongly correlated quantum matter. However, interpreting measurement outcomes in such systems poses significant challenges. Here, we present a theoretical framework for information extraction in synthetic quantum matter, illustrated for the case of a quantum quench in a spinor Bose-Einstein condensate experiment. Employing nonparametric unsupervised learning tools that provide different measures of information content, we demonstrate a theory-agnostic approach to identify dominant degrees of freedom. This enables us to rank operators according to their relevance, akin to effective field theory. To characterize the corresponding effective description, we then explore the intrinsic dimension of data sets as a measure of the complexity of the dynamics. This reveals a simplification of the data structure, which correlates with the emergence of time-dependent universal behavior in the studied system. Our assumption-free approach can be immediately applied in a variety of experimental platforms.

We investigate superconducting transport in the DC field induced Wannier-Stark flat bands in the presence of interactions. Flat bands offer the possibility of unconventional high temperature superconductivity, where the superfluid weight, $D_s$, is enhanced by the density overlap of the localized states. However, construction of flat bands typically requires very precise tuning of Hamiltonian parameters. To overcome this difficulty, we propose a feasible alternative to realize flat bands by applying a DC field in a commensurate lattice direction. We systematically characterize the superconducting behavior on these flat bands by studying the effect of the DC field and attractive Hubbard interaction strengths on the wave function, correlation length, pairing order parameter, and the superfluid weight $D_s$. Our main result is that the superfluid weight is dramatically enhanced at an optimal value of the interaction strength and weak DC fields.

We report on magnetotransport and thermoelectric properties of two ternary carbides ${\mathrm{HoNiC}}_2$ and ${\mathrm{ErNiC}}_2$ hosting both charge density wave and long-range magnetic order. In the charge density wave state, both compounds show relatively large magnetoresistance MR $\approx$ 150% in ${\mathrm{HoNiC}}_2$ and $\approx 70$% in ${\mathrm{ErNiC}}_2$ at a magnetic field of 9 T and temperature as low as 2 K. This positive field-linear magnetoresistance shows no signatures of saturation. Our combined analysis of diagonal and off-diagonal transport responses reveals electronic mobility values on the order of ${10}^3{\mathrm{cm}}^2{\mathrm{V}}^{-1}{\mathrm{s}}^{-1}$ at 2 K. Both the elevated mobility and related enhanced magnetoresistance persist in the zero-field antiferromagnetic ground state and survive the field-induced crossovers through metamagnetic to field-aligned ferromagnetic states. The robustness of the high-mobility Fermi surface pockets across the magnetically ordered states suggests that the charge density wave is not suppressed but coexists with long-range magnetism in the entire dome of the magnetically ordered states.

We report the magnetotransport, Shubnikov–de Haas (SdH), and de Haas–van Alphen (dHvA) quantum oscillation studies on a high-quality ${\mathrm{ZrAs}}_2$ single crystal grown by the flux method. The temperature-dependent resistivity $\rho \left(T\right)$ shows a metallic behavior in zero field, whereas there is an upturn in resistivity in the presence of high magnetic fields. Large magnetoresistance ($1010\%$ for $I\left|\right|\left[010\right], B\left|\right|\left[105\right]$ and $800\%$ for $I\left|\right|\left[101\right], B\left|\right|\left[010\right]$) with quadratic field dependence is observed without any sign of saturation up to the 14 T magnetic field. The carrier concentration is estimated from the field-dependent Hall resistivity, and it is found that the charge carriers are nearly compensated which results in such large magnetoresistance. Six main frequencies 18 T (${\beta }_1$), 325 T (${\beta }_2$), 428 T (${\beta }_3$), 436 T (${\beta }_4$), 575 T (${\beta }_5$), and 1160 T ($\alpha$) are identified from dHvA oscillation for $B\left|\right|\left[010\right]$, which are in good agreement with theoretically calculated frequencies. We also observe a large anisotropic magnetoresistance (about $88\%, 71\%$, and $67\%$ at 14 T and 2 K for the three different orientations) and the planar Hall effect in ${\mathrm{ZrAs}}_2$.

We introduce a method based on the auxiliary master equation for solving the problem of an impurity with local electron-electron and electron-phonon interaction embedded between two conduction leads with a finite-bias voltage. The Anderson-Holstein Hamiltonian is transformed to a corresponding Lindblad equation with a reduced set of sites, providing an optimal approximation of the hybridization function. The problem is solved in the superfermion representation, using a configuration interaction for fermions and bosons. The phonon basis is shifted and rotated with the intention of permitting a low phonon basis cutoff, even in the strong-coupling regime. We benchmark this approach with the numerical renormalization group in equilibrium, finding excellent agreement. We observe, however, that the rotation brings no advantage beyond the bare shift. This is even more apparent out of equilibrium, where issues in convergence with respect to the size of the phononic Hilbert space occur only in the rotated basis. As an application of the method, we explore the evolution of the phononic peak in the differential conductance spectra with changing phonon frequency.

We report on scanning tunneling microscopy and spectroscopy studies of the slightly underdoped cuprate superconductor ${\mathrm{HgBa}}_2{\mathrm{Ca}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{8+\delta }$, which has an onset $T_c\approx 120$ K. Disordered HgO-terminated surfaces were observed after sample cleaving in ultrahigh vacuum, revealing spatially inhomogeneous energy gaps with a low-lying $\mathsf{V}$-shaped structure and the ubiquitous mode features. Similar to Bi-family cuprate superconductors, vortex cores were identified by the suppression of superconducting coherence peaks and the emergence of in-gap features. Superconductivity near step edges is also strongly suppressed over several coherence lengths, forming an effective interface to the superconducting region, where the local spectra show a weak zero-bias conductance peak arising from the Andreev bound states. These results are expected from the widely believed $d$-wave nature in cuprates, demonstrating a platform for studying unconventional superconductivity.

Dynamical mean field theory allows access to the physics of strongly correlated materials with nontrivial orbital structure, but relies on the ability to solve auxiliary multiorbital impurity problems. The most successful approaches to date for solving these impurity problems are the various continuous time quantum Monte Carlo algorithms. Here, we consider perhaps the simplest realization of multiorbital physics: the bilayer Hubbard model on an infinite-coordination Bethe lattice. Despite its simplicity, the majority of this model's phase diagram cannot be predicted by using traditional Monte Carlo methods. We show that these limitations can be largely circumvented by recently introduced inchworm Monte Carlo techniques. We then explore the model's phase diagram at a variety of interaction strengths, temperatures, and filling ratios.

We study interlayer pairing of composite fermions in the total $\nu =1/2+1/2$ quantum Hall bilayer as a possible framework for understanding the experimentally observed transition from a compressible state at large layer spacing to a bilayer quantum Hall state at small layer spacing in this system. We consider a model in which the effective interlayer composite fermion pairing interaction mediated by the Chern-Simons gauge fields in the two layers is singular with both attractive (out-of-phase) and repulsive (in-phase) components diverging at low frequency. If only the more singular attractive interaction is included the pairing gap obtained by solving the gap equation is proportional to the inverse of the layer spacing squared. In the so-called local approximation, we find that when the less singular repulsive interactions are also included the pairing gap still falls off as inverse layer spacing squared, consistent with recent analyses, but is strongly suppressed to a degree that may account for the fact that this predicted inverse square dependence is not observed experimentally. The analytically obtained local approximation solutions are then used as a starting point to numerically iterate the full gap equation to assess the validity of the approximation in this limit.

We have demonstrated the possibility to control the otherwise robust magnetic properties of transition-metal phosphorus trisulfides ($\text{Mn/Fe}\text{/}\mathrm{NiP}{\mathrm{S}}_3$) in their heterostructures with Weyl semimetallic $\mathrm{Mo}{\mathrm{Te}}_2$ which can be attributed to the Dzyaloshinskii-Moriya (DM) interactions at the interface of the two materials. While the DM interaction is known to scale with the strength of the spin-orbit coupling (SOC), we demonstrate using experiments on heterostructures with a variety of substrates (underlayers) hosting variable SOC and electronic density of states (DOS) that the effect of DM interaction strongly varies with the electronic DOS of the SOC-hosting layer as well as the spin orientation and degree of anisotropy associated with the magnetic layer.

Interference gating or iGate is a unique method for ultrafast time-resolved electron holography in a transmission electron microscope enabling a spatiotemporal resolution in the $\mathrm{nm}$ and $\mathrm{ns}$ regime with a minimal technological effort. Here, iGate is used for the first image-based investigation of the local dynamics of the projected electric potential in the area of the space-charge region of two different general purpose silicon diodes during switching between unbiased and reverse-biased condition with a temporal resolution of $25\mathrm{ns}$ at a repetition rate of $3\mathrm{M}\mathrm{Hz}$. The obtained results for a focus-ion-beam-prepared ultrafast UG1A rectifier diode, which shows a decreasing capacitance with increasing reverse bias are in good agreement with an electric characterization of the macroscopic device as well as with theoretical expectations. For a severely modified 1N4007 device, however, time-resolved electron holography revealed a MOSCAP-like behavior with a rising capacitance in the area of the space-charge region during the switching into reverse-biased condition. Remarkably, a different behavior, dominated by the effective capacitance of the electrical setup, can be observed in the vacuum region outside both devices within the same measurements, clearly showing the benefits of localized dynamic potentiometry.

A recent study [R. Hanai et al., Phys. Rev. Lett. 122, 185301 (2019)] highlighted a first-order-like dissipative phase transition in a two-component quantum system with an exceptional point coinciding with the phase boundary endpoint. Here, we show a disparity between the exceptional point and the endpoint which is closely connected to the stability of solutions. We present a general phase diagram describing different phases in a generic nonlinear binary system. The phase transition may occur also in the regime of weak coupling between the modes, which was excluded previously. In a certain range of parameters, the system converges to a limit cycle, which vanishes at the exceptional point. Our results emphasize the connection between phase transitions, bistability, and exceptional points of non-Hermitian nonlinear systems in general, providing insight into strongly coupled light-matter systems in particular.

Topological transitions unveil a fundamentally novel pathway of research, revealing captivating optical phenomena in electromagnetic metamaterials. In this work, we give comprehensive pictures of topological phase diagrams and topological transitions in the gyromagnetic metamaterials (GMs). We comprehensively demonstrate the topology of all types of equifrequency surfaces of the GMs. The Weyl points and the nodal line can coexist in the GMs, and they are the critical points in the topological transitions. The localized Fermi arc surface states exist at the boundary between the vacuum state and GMs owing to the bulk-edge correspondence of the material system. Full-wave simulations reveal that topological surface waves can smoothly transmit forward around the square defect without reflection or scattering. Remarkably, different types of topological beam splitters are demonstrated utilizing the topological surface waves in the GMs. We theoretically demonstrate that the physical mechanism of achieving the topological beam splitters is caused by different group velocity directions of the Fermi arcs surface states of the material system. Moreover, the topological wave division and controllable propagation of the Fermi arc surface states can be achieved by adopting the different boundary configurations and gyromagnetic parameters in the topological beam splitters. Our work could broaden insights into topological wave physics and provide more flexibility for photonic devices in the electromagnetic media.

We propose a 3D topolectrical network that can be tuned to realize various higher-order topological gapless and chiral phases. We first study a higher-order Dirac semimetal phase that exhibits a hinge-like Fermi arc linking the Dirac points. This circuit can be extended to host highly tunable first- and second-order Weyl semimetal phases by introducing a nonreciprocal resistive coupling in the $x\text{−}y$ plane that breaks time reversal symmetry. The first- and second-order Weyl points are connected by zero-admittance surface and hinge states, respectively. We also study the emergence of first- and second-order chiral modes induced by resistive couplings between similar nodes in the $z$ direction. These modes, respectively, occur in the midgap of the surface and hinge admittance bands in our circuit model without the need for any external magnetic field.

We study a unique form of metallic ferromagnetism in which orbital moments surpass the role of spin moments in shaping the overall magnetization. This system emerges naturally upon doping a topologically nontrivial Chern band in the recently identified quarter metal phase of rhombohedral trilayer graphene. Our comprehensive scan of the density-interlayer potential parameter space reveals an unexpected landscape of orbital magnetization marked by two sign changes and a line of singularities. The sign change originates from an intense Berry curvature concentrated close to the band edge and the singularity arises from a topological Lifshitz transition that transforms a simply connected Fermi sea into an annular Fermi sea. Importantly, these variations occur while the ground-state order parameter (i.e., valley and spin polarization) remains unchanged. This unconventional relationship between the order parameter and magnetization markedly contrasts traditional spin ferromagnets, where spin magnetization is simply proportional to the ground-state spin polarization via the gyromagnetic ratio. We compute energy and magnetization curves as functions of collective valley rotation to shed light on magnetization dynamics and to expand the Stoner-Wohlfarth magnetization reversal model. We provide predictions on the magnetic coercive field that can be readily tested in experiments. Our results challenge established perceptions of magnetism, emphasizing the important role of orbital moments in two-dimensional materials such as graphene and transition metal dichalcogenides and, in turn, expand our understanding and potential manipulation of magnetic behaviors in these systems.