The observations of persistent revivals in the Rydberg atom chain have revealed a weak ergodicity breaking mechanism known as quantum many-body scars, which is typically a collection of states with low entanglement embedded in otherwise thermal spectra. Here, by applying a generic formalism, we reveal a direct evolution from the quantum many-body scars to the multiple inverted quantum many-body scars, i.e., different sets of excited states with volume-law entanglement entropy embedded in a sea of states with area-law entanglement. When increasing the disorder strength, a series of exact eigenstates, acting as conventional quantum many-body scars in a regime of weak disorder, remain unchanged. Around each of these states, the inverted quantum many-body scars are introduced by the increased disorder. Moreover, the strong disorder also gives rise to additional sets of inverted quantum many-body scars with their energies concentrating in the middle of the exact eigenstates. As a result, all the multiple inverted quantum many-body scars are approximately equidistant in energy, reminiscent of conventional quantum many-body scarred states. Despite being the measure-zero states in the whole spectrum, these inverted quantum many-body scarred states significantly influence nonequilibrium dynamics in the large disorder regime. Random thermal states in a specific subspace show periodic revivals in the fidelity dynamics, while the typical charge-density-wave states exhibit persistent imbalance dynamics. We further examine the stability of the conventional and the inverted quantum many-body scars against the external random field. Our findings expand the variety of nonthermal systems and draw a connection between the weak violation of ergodicity and that of nonergodicity.

With increasing performance of actual qubit devices, even subtle effects in the interaction between qubits and environmental degrees of freedom become progressively relevant and experimentally visible. This applies particularly to the timescale separations that are at the basis of the most commonly used numerical simulation platform for qubit operations, namely, the conventional Lindblad master equation (LE): the Markov approximation and the rotating wave approximation (RWA). In this contribution, we shed light on the questions (i) to which extent it is possible to monitor violations of either of these timescale separations experimentally and (ii) which of them is the most severe to provide highly accurate predictions within (approximate) numerical schemes in relevant parameter ranges. For this purpose, we compare three simulation methods for the reduced density matrix with progressively growing accuracy. In particular, predictions for relaxation and decoherence of a qubit system in the presence of reservoirs with Ohmic and sub-Ohmic spectral densities are explored and, with the aid of proper protocols based on Ramsey experiments, the role of non-Markovianity and RWA are revealed. We discuss potential implications for future experiments and the design of approximate yet accurate numerical approaches.

Using first-principles calculations we investigate the intrinsic origins of the anomalous Hall effect (AHE) and the anomalous Nernst effect (ANE) in antiperovskite ferrimagnet ${\mathrm{Mn}}_4\mathrm{N}$. We predict that the AHE is significantly enhanced under both compressive and tensile strain; however, the ANE generally decreases under epitaxial strain, except for 1% compressive strain. We connect this behavior to the evolution of the Berry curvature with strain, suggesting similar strategies for achieving large AHE and ANE changes with modest amounts of strain. Finally, we find that the nonmonotonic characteristics of the AHE and ANE stem from the formation and movement of new Weyl points at the periphery of the Brillouin zone under compressive and tensile strains.

${\mathrm{Eu}}_5{\mathrm{In}}_2{\mathrm{Sb}}_6$ is an orthorhombic nonsymmorphic small band gap semiconductor with three distinct ${\mathrm{Eu}}^{2+}$ sites and two low-temperature magnetic phase transitions. The material displays one of the greatest (negative) magnetoresistances of known stoichiometric antiferromagnets and belongs to a family of Zintl materials that may host an axion insulator. Using single crystal neutron diffraction, we show that the $T_{\mathrm{N}1}=14\mathrm{K}$ second-order phase transition is associated with long-range antiferromagnetic order within the chemical unit cell $({\mathbf{k}}_1=\left(000\right))$. Upon cooling below $T_{\mathrm{N}1}$, the relative sublattice magnetizations of this structure vary until a second-order phase transition at $T_{\mathrm{N}2}=7\mathrm{K}$ that doubles the unit cell along the $\widehat{\mathbf{c}}$ axis $({\mathbf{k}}_2=\left(00\frac{1}{2}\right))$. We show the anisotropic susceptibility and our magnetic neutron diffraction data are consistent with magnetic structures described by the ${\mathrm{\Gamma }}_3$ irreducible representation with the staggered magnetization of the ${\mathbf{k}}_1$ and ${\mathbf{k}}_2$ components polarized along the $\widehat{\mathbf{b}}$ and $\widehat{\mathbf{a}}$ axis, respectively. As the ${\mathbf{k}}_2$ component develops, the amplitude of the ${\mathbf{k}}_1$ component is reduced, which indicates a $2\mathbf{k}$ noncollinear magnetic structure. Density functional theory is used to calculate the energies of these magnetic structures and to show the ${\mathbf{k}}_1$ phase is a metal so $T_{\mathrm{N}1}$ is a rare example of a unit-cell-preserving second-order phase transition from a paramagnetic semiconductor to an antiferromagnetic metal. DFT indicates the transition at $T_{\mathrm{N}2}$ to a doubled unit cell reduces the carrier density of the metal.

${\mathrm{TbMn}}_6{\mathrm{Sn}}_6$ is a correlated topological magnet with a Mn-based kagome lattice, in which a Chern gap opens at the Dirac point at low temperatures. The magnetic moment direction of the ferrimagnetic order changes from in the kagome plane to out-of-plane upon cooling, which is essential for generating the Chern gap, but the underlying mechanism for the spin reorientation remains elusive. Here, we investigate the spin-reorientation transition in ${\mathrm{TbMn}}_6{\mathrm{Sn}}_6$ using neutron scattering. We provide direct evidence for the spin-reorientation transition and unveil the coexistence of two Tb modes at 200 K. To account for these results, we put forward a model based on SU(N) spin-wave theory, in which there is a temperature evolution of the ground state Tb $4f$ orbitals, driven by the crystalline electric field, single-ion anisotropy, and exchange interactions between Tb and Mn ions. Our findings shed light on the complex magnetism of ${\mathrm{TbMn}}_6{\mathrm{Sn}}_6$, despite its relatively simple ground state magnetic structure, and provide insights into the mechanisms for tuning magnetic topological materials.

We show that a skyrmion in a classical bipartite antiferromagnetic lattice can be spatially displaced in a controlled manner by externally applied spin waves. We reveal the relation between the skyrmion motion and the spin wave properties. To this end, we derive a classical spin wave formalism, which is tailored to the antiferromagnetic two-dimensional square lattice. The antiferromagnetic spin waves can be classified into two types with respect to their polarization, with two modes each. The circularly polarized spin waves oscillate with different amplitudes in the respective sublattices and induce a skyrmion Hall effect. The two modes are symmetric under sublattices exchange and determine the overall sign of the Hall angle. For linearly polarized spin waves, the two sublattices oscillate elliptically in opposite direction, however, with the same amplitude. These accelerate the skyrmion solely into their own propagation direction. The two modes are symmetric under component $x-y$ exchange and impact Bloch or Néel skyrmions differently. Our results indicate possible technical applications of spin wave driven skyrmion motion. As one example we propose a racetrack where spin waves pump skyrmions along the track in antiferromagnets.

The compounds $\mathit{Ln}{\mathrm{AuAl}}_4{\mathrm{Ge}}_2$ ($\mathit{Ln}=$ lanthanide) form in a structure that features two-dimensional triangular lattices of $\mathit{Ln}$ ions that are stacked along the crystalline $c$ axis. Together with crystal electric field effects, magnetic anisotropy, and electron-mediated spin exchange interactions, this sets the stage for the emergence of strongly correlated spin and electron phenomena. Here we investigate ${\mathrm{SmAuAl}}_4{\mathrm{Ge}}_2$, which exhibits weak paramagnetism that strongly deviates from conventional Curie-Weiss behavior. Complex antiferromagnetic ordering emerges at $T_{\mathrm{N}1}=13.2\mathrm{K}$ and $T_{\mathrm{N}2}=7.4\mathrm{K}$, where heat capacity measurements show that these transitions are first and second order, respectively. These measurements also reveal that the Sommerfeld coefficient is not enhanced compared to the nonmagnetic analog ${\mathrm{YAuAl}}_4{\mathrm{Ge}}_2$, consistent with the charge carrier quasiparticles exhibiting typical Fermi liquid behavior. The temperature-dependent electrical resistivity follows standard metallic behavior, but linear magnetoresistance unexpectedly appears within the ordered state. We compare these results to other $\mathit{Ln}{\mathrm{AuAl}}_4{\mathrm{Ge}}_2$ materials, which have already been established as localized $f$-electron magnets that are hosts for interesting magnetic and electronic phases. From this, ${\mathrm{SmAuAl}}_4{\mathrm{Ge}}_2$ emerges as a complex quantum spin metal, inviting further investigations into its properties and the broader family of related materials.

We provide bulk transport evidence for twin-boundary pinning of vortices in FeSe. We measure interlayer resistance in FeSe in magnetic fields and find that, as the field is rotated in the $ab$ plane, the flux-flow resistivity is suppressed when the field direction is parallel to twinning planes. The width of the associated dip in the resistance vs in-plane field direction curve varies as $T^{1/2}{B}^{-3/4}$, consistent with the creation of kinked vortices near the parallel field geometry.

Corner-localized states represent intriguing aspects of higher-order topological systems. Despite their importance, the topological invariant that distinguishes between zero-energy and non-zero-energy corner states has received limited attention in the literature. Therefore, we introduce “modified multipole chiral numbers,” utilizing the 2-norm of the pseudo wave vector to characterize zero-energy corner states and to categorize the topological phase in chiral-symmetric two-dimensional and one-dimensional systems. The quantified topological invariant, protected by chiral symmetry, is associated with the quantity and spatial distribution of the zero-energy corner states. Theoretical analyses were conducted using multiple models, and both simulations and experimental data gathered from honeycomb lattices in acoustic systems corroborate these insights. These results offer valuable guidelines for designing systems that feature topologically protected corner states across various platforms and open avenues for the exploration of boundary-obstructed topological phases.

We investigated the correlation between crystal structures and spin states of cobalt perovskites ${\mathrm{La}}_{1-x}{\mathrm{Pr}}_x{\mathrm{CoO}}_3$ $(x=0.30, 0.34)$ by x-ray powder diffraction, transmission electron microscopy, and magnetic measurements at low temperatures. The $x=0.30$ and $x=0.34$ compounds exhibit structural phase transitions between a low-temperature orthorhombic phase (Pbnm) and a high-temperature rhombohedral phase $\left(R\overline{3}c\right)$ at around 170 and 250 K, respectively. In fairly wide temperature ranges around these temperatures, the low-temperature phase and the high-temperature phase coexist. The contribution of ${\mathrm{Co}}^{3+}$ ions to magnetic susceptibility approaches zero with decreasing temperatures. This indicates that low-spin cobalt ions increased at low temperatures. The ${\mathrm{CoO}}_6$ octahedron in the low-temperature orthorhombic phase shows an almost isotropic one in low temperatures, but changes to an anisotropic one as the temperature rises until the phase transition temperature. This suggests that the intermediate-spin state gradually develops from the low-temperature dominant low-spin state with increasing temperature. We also observed small anomalies in the magnetic susceptibility of each compound in the vicinity of the structural phase transition temperature.

Many-body localization in disordered systems in one spatial dimension is typically understood in terms of the existence of an extensive number of (quasi) local integrals of motion (LIOMs) which are thought to decay exponentially with distance and interact only weakly with one another. By contrast, little is known about the form of the integrals of motion in disorder-free systems which exhibit localization. Here, we explicitly compute the LIOMs for disorder-free localized systems, focusing on the case of a linearly increasing potential. We show that while in the absence of interactions, the LIOMs decay faster than exponentially, the addition of interactions leads to the formation of a slow-decaying plateau at short distances. We study how the localization properties of the LIOMs depend on the linear slope, finding that there is a significant finite-size dependence, and present evidence that adding a weak harmonic potential does not result in typical many-body localization phenomenology. By contrast, the addition of disorder has a qualitatively different effect, dramatically modifying the properties of the LIOMS.

We report on the quantum criticality of ${\mathrm{YbCu}}_4\mathrm{Ni}$ as revealed by our combined micro- and macro-measurements. We determine the crystal structure of ${\mathrm{YbCu}}_4\mathrm{Ni}$ with site mixing by neutron diffraction measurements, which suggests the possible presence of Kondo disorder. However, decreasing the local spin susceptibility distribution and the development of spin fluctuations below 10 K at ambient pressure by muon spin rotation and relaxation measurements suggests that ${\mathrm{YbCu}}_4\mathrm{Ni}$ exhibits quantum criticality. Therefore, our experimental results indicate that ${\mathrm{YbCu}}_4\mathrm{Ni}$ is a material that exhibits quantum criticality under zero magnetic field and ambient pressure.

We study the theoretical model of a ferromagnetic semiconductor as a system of randomly distributed Ising spins with a long-range exchange interaction. Using the density-of-states approach, we analytically obtain the magnetic susceptibility and heat capacity over a wide range of temperatures and magnetic fields. It is shown that the finite system of spins in magnetic field less than a certain critical field is in a superparamagnetic state due to thermodynamic fluctuations. The complex phase structure of a ferromagnetic semiconductor is discussed.

The recently discovered $(\mathrm{Ba},\mathrm{Sr}){\mathrm{Ni}}_2{\mathrm{As}}_2$ family provides an ideal platform for investigating the interaction between electronic nematicity and superconductivity. Here, we report the muon spin relaxation $\left(\mu \mathrm{SR}\right)$ measurements on ${\mathrm{BaNi}}_2{\mathrm{As}}_2$. Transverse-field $\mu \mathrm{SR}$ experiments indicate that the temperature dependence of superfluid density is best fitted with a single-band $s$-wave model. On the other hand, the magnetic penetration depth $\lambda$ shows magnetic field dependence, which contradicts the single-band fully gapped scenario. Zero-field $\mu \mathrm{SR}$ experiments indicate the absence of spontaneous magnetic field in the superconducting state, showing the preservation of time-reversal symmetry in the superconducting state. Our $\mu \mathrm{SR}$ experiments suggest that ${\mathrm{BaNi}}_2{\mathrm{As}}_2$ is a fully gapped multiband superconductor. The superconducting gap amplitudes of each band are nearly the same while different bands exhibit different coherence lengths. The present work helps to elucidate the controversial superconducting property of this parent compound, paving the way for further research on doping the system with Sr to enhance superconductivity.

The effect of 3 MeV proton irradiation on the superconductivity of ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$ and $\mathrm{Cs}{\left({\mathrm{V}}_{0.93}{\mathrm{Nb}}_{0.07}\right)}_3{\mathrm{Sb}}_5$ has been investigated by resistivity and magnetization measurements. The critical transition temperature $T_{\mathrm{c}}$ increases from 3.2 to 4.4 K after proton irradiation for ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$ single crystals. Besides the enhanced critical current density, we observe a broad magnetization peak in the proton-irradiated ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$ single crystals, which can be attributed to the enhancement of vortex pinning induced by irradiation. We find the magnetization peak close to the upper critical field $H_{\mathrm{c}2}$ in $\mathrm{Cs}{\left({\mathrm{V}}_{0.93}{\mathrm{Nb}}_{0.07}\right)}_3{\mathrm{Sb}}_5$ single crystals, which should come from the softening of the flux line lattice. The $T_{\mathrm{c}}$ is slightly suppressed after proton irradiation in $\mathrm{Cs}{\left({\mathrm{V}}_{0.93}{\mathrm{Nb}}_{0.07}\right)}_3{\mathrm{Sb}}_5$ single crystals at the present irradiation doses. The vortex phase diagrams have been constructed for the kagome superconductors $\mathrm{Cs}{\left({\mathrm{V}}_{0.93}{\mathrm{Nb}}_{0.07}\right)}_3{\mathrm{Sb}}_5$ and proton-irradiated ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$ based on the obtained data.

The effects of 2.5-MeV electron irradiation were studied in the superconducting phase of single crystals of ${\mathrm{LaNiGa}}_2$, using measurements of electrical transport and radio-frequency magnetic susceptibility. The London penetration depth is found to vary exponentially with temperature, suggesting a fully gapped Fermi surface. The inferred superfluid density is close to that of a single-gap weak-coupling isotropic $s\text{−}\mathrm{wave}$ superconductor. Superconductivity is extremely robust against nonmagnetic point-like disorder induced by electron irradiation. Our results place strong constraints on the previously proposed triplet pairing state by requiring fine-tuned impurity scattering amplitudes and are most naturally explained by a sign-preserving, weak-coupling, and approximately momentum-independent singlet superconducting state in ${\mathrm{LaNiGa}}_2$, which does not break time-reversal symmetry. We discuss how our findings could be reconciled with previous measurements that indicated magnetic signatures in the superconducting phase.

Accessing the physics of strongly coupled metals in a controlled way is a challenging problem in theoretical condensed matter physics. In this paper, we revisit the possibility of understanding strongly coupled metals through a holographic duality with a weakly coupled gravitational theory in one higher dimension (i.e., a suitable generalization of the “AdS/CFT duality”). Previous attempts at devising holographic models of strongly coupled metals have suffered from drawbacks; for example, many such models do not even seem to be able to describe a Fermi surface that satisfies Luttinger's theorem, which is ought to be a core requirement in any physically reasonable model of a metal. Here, we propose a radically different approach to constructing holographic models of strongly coupled metals. The idea is that for applications, it should be sufficient to construct a holographic dual of the effective field theory that controls the infrared physics of the metal. We invoke recent paper that has identified a precise criterion for such an effective field theory to be “emergeable” from a continuum ultraviolet (UV) theory at nonzero charge density (or its equivalent in lattice models, namely an incommensurate charge filling). We show that imposing this criterion leads to a holographic model of a strongly coupled metal with physically reasonable properties, including a Fermi surface satisfying Luttinger's theorem. We discuss a possible physical interpretation of our results.

When an electron beam hits an interface at a point, the reflection beam comes back from another interface point and a reflection shift occurs in real space. We investigate the reflection shift evolution and Fermi arcs on the interface between two Multifold Weyl semimetals by changing the system parameters continuously using tight-binding calculations. The incident pocket is touched tangentially by Fermi arcs through reflection shift vortices located on the pocket edge. When the transmissive pocket is changed by tuning the parameters of the transmissive side, the edge vortex is shifted to inner locations by the transmissive pocket covering it. In the intersection region between the two pockets, the vortex and antivortex pair can be created and annihilated. The net number of vortices in the incident pocket for any case and that in the transmissive pocket if the reflection shift can be defined there, are just the monopole topological charges of the incident and transmissive media, respectively. Our work uncovers new quantized features of interfaces between topological materials.

Understanding the interaction mechanics between graphene layers and coaxial carbon nanotubes (CNTs) is essential for modeling graphene and CNT-based nanoelectromechanical systems. This work proposes a new continuum contact model to study interlayer interactions between curved graphene sheets. The continuum model is calibrated and validated using molecular dynamics (MD) simulations. These are carried out employing the reactive empirical bond order (REBO)$+$Lennard-Jones (LJ) potential to model the interactions within a sheet, while the LJ, Kolmogorov-Crespi (KC), and Lebedeva potentials are used to model the interactions between sheets. The continuum contact model is formulated for separation distances greater than 0.29 nm, when sliding contact becomes nondissipative and can be described by a potential. In this regime, sheet deformations are sufficiently small and do not affect the sheet interactions substantially. This allows to treat the master contact surface as rigid, thus simplifying the contact formulation greatly. The model calibration is conducted systematically for a sequence of different stackings using existing and newly proposed ansatz functions. The calibrated continuum model is then implemented in a curvilinear finite-element (FE) shell formulation to investigate the pull-out and twisting interactions between coaxial CNTs. The resisting pull-out forces and torques depend strongly on the chirality of the considered CNTs. The absolute differences between FE and MD results are very small and can be attributed to model assumptions and loading conditions.