Unraveling the mechanisms of ergodicity breaking in complex quantum systems is a central pursuit in nonequilibrium physics. In this work, we investigate a one-dimensional spin-1 model featuring a tunable long-range hopping term, $H_n$, which introduces nonlocal interactions and bridges the gap between Hermitian and non-Hermitian regimes. Through a systematic analysis of level-spacing statistics and Krylov complexity, we demonstrate that $H_n$ acts as a universal control parameter driving the transition from integrability to quantum chaos. Specifically, increasing the strength of $H_n$ induces a crossover from Poissonian to Gaussian orthogonal ensemble statistics in the Hermitian limit and similarly triggers chaotic dynamics in the non-Hermitian case. Most remarkably, despite the onset of global chaos, we identify a tower of exact nonthermal eigenstates that evade thermalization. These states survive as robust quantum many-body scars, retaining low entanglement and coherent dynamics even under strong non-Hermitian perturbations. Our findings reveal a universal mechanism by which long-range and non-Hermitian effects reshape quantum ergodicity, offering pathways for preserving quantum coherence in complex many-body systems.

Changes in magnetic dynamical characteristics accompanying slowing of spin relaxation below 100 K and freezing of spins detected by muon and neutron diffractions have been found. Magnetic phases identified in CrSBr single crystals by slow magnetization relaxation are caused by stepwise changes in magnetic field, alternating current (ac) magnetic susceptibility, and recording of the first-order reversal curve (FORC). “Slow” magnetic relaxation $\sim {10}^3$ s and FORC highlight spin transition effect on magnetic viscosity and domain dynamics. Below 40 K magnetization reversal is due to nucleation, while above 100 K domain propagation is origin of magnetization reversal. ac susceptibility in the 1- to 100-ms time window indicates gradual temperature-dependent changes in the frequency-independent susceptibility peak, identifying both the Néel temperature ($T_{\mathrm{N}}=132\mathrm{K}$) and thermal fluctuation slowing in the 40 K to 100 K range. Field-dependent magnetic susceptibility indicates spin-flop transitions from the antiferromagnetic to the canted state and to ferromagnetic spin configuration. Changes in magnetization reversal mechanism accompanying spin freezing highlight contribution of spin dynamics and spin relaxation to domain wall dynamics.

Transition metal dichalcogenides (TMDs) enable magnetic property engineering via intercalation, but stoichiometry-structure-magnetism correlations remain poorly defined for Fe-intercalated ${\mathrm{NbSe}}_2$. Here, we report a systematic study of ${\mathrm{Fe}}_x{\mathrm{NbSe}}_2$ across an extended composition range $0.05\le x\le 0.38$, synthesized via chemical vapor transport and verified by rigorous energy-dispersive x-ray spectroscopy (EDS) microanalysis. X-ray diffraction, magnetic, and transport measurements reveal an intrinsic correlation between Fe content, structural ordering, and magnetic ground states. With increasing $x$, the system undergoes a successive transition from paramagnetism to a spin-glass state, then to long-range antiferromagnetism (AFM), and ultimately to a reentrant spin-glass phase, with the transition temperatures exhibiting a nonmonotonic dependence on Fe content. The maximum Néel temperature ($T_{\mathrm{N}}=175\mathrm{K}$) and strongest AFM coupling occur at $x=0.25$, where Fe atoms form a well-ordered $2a_0\times 2a_0$ superlattice within van der Waals gaps. Beyond $x=0.25$, the superlattice transforms or disorders, weakening Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions and significantly reducing $T_{\mathrm{N}}$. Electrical transport exhibits distinct anomalies at magnetic transition temperatures, corroborating the magnetic state evolution. Our work extends the compositional boundary of Fe-intercalated ${\mathrm{NbSe}}_2$, establishes precise stoichiometry-structure-magnetism correlations, and identifies structural ordering as a key tuning parameter for AFM. These findings provide a quantitative framework for engineering altermagnetic or switchable antiferromagnetic states in van der Waals materials.

The phase diagram and spin excitation spectra of the Kitaev-Heisenberg model with bond anisotropy are investigated using the exact diagonalization algorithm and spin cluster perturbation theory. By adjusting the model parameters and anisotropy intensity, we comprehensively map the complete phase diagram and uncover the excitation spectral characteristics of each phase. Besides the Kitaev spin liquid phases, whose excitation spectra appear entirely as a continuum, the antiferromagnetic Néel and zigzag phases also display strong high-energy continua and significant renormalization of the magnon dispersions. In contrast, the magnon dispersions of the ferromagnetic and stripy phases align closely with the predictions of linear spin-wave theory. Bond anisotropy induces directional selectivity of the magnetic moments in the four magnetically ordered phases, depending on the interaction parameters. Furthermore, bond anisotropy lifts the gaplessness of the pseudo-Goldstone mode for magnetization along the $z$ axis, while maintaining the gapless nature for magnetization perpendicular to the $z$ axis. Our results demonstrate that quantum fluctuations do not destroy the gapless property, which may be inherited from the gapless phase in the one-dimensional limit, described by a conformal field theory with central charge $c=1$.

We investigate the possibility of engineering dissipatively long-range order that is robust against heating in strongly interacting fermionic systems, relevant for atoms in cavity QED. It was previously shown [Tindall et al. Phys. Rev. Lett. 123, 030603 (2019)] that it is possible to stabilize long-range order in a Hubbard model by exploiting a dissipative mechanism in the Lindblad limit, this latter being valid for spectrally unstructured baths. Here, we first show that this mechanism still holds when including additional spin-exchange interactions in the model, that is, for the tUJ model. Moreover, by means of a Redfield approach that goes beyond the Lindblad case, we show how the stability of the engineered state depends crucially on properties of the bath spectral density and discuss the feasibility of those properties in an experiment.

In this study, we report the fractional magnetization plateaus and anomalous Hall effect in a newly synthesized kagome intermetallic magnet, $\mathrm{C}{\mathrm{e}}_3\mathrm{MgB}{\mathrm{i}}_5$. In this compound, the Ce atoms form a distorted kagome lattice, which allows for strong magnetic frustration by Ruderman-Kittel-Kasuya-Yosida interaction. Single-crystal neutron diffraction shows a nontrival magnetic ground state consisting of both all-in–all-out (aiao) spins and 2-in-1-out–1-in-2-out (2i1o–1i2o) spins below $T_{\mathrm{N}}=4.5\mathrm{K}$. By applying a magnetic field, two magnetization plateaus are found at $M/M_{\mathrm{s}}=1/3$ and $M/M_{\mathrm{s}}=1/2$. Transport measurements on $\mathrm{C}{\mathrm{e}}_3\mathrm{MgB}{\mathrm{i}}_5$ unveil a pronounced nonmonotonic magnetoresistance and a significant anomalous Hall effect, which are indicative of a strong correlation between its magnetic and electronic properties. Meanwhile, an obvious Kondo effect is observed in $\mathrm{C}{\mathrm{e}}_3\mathrm{MgB}{\mathrm{i}}_5$. These results suggest that $\mathrm{C}{\mathrm{e}}_3\mathrm{MgB}{\mathrm{i}}_5$ is a promising platform to explore the exotic quantum ground state.

The remarkable mechanical properties of high- and medium-entropy alloys are closely related to their complex atomic-scale chemical environments. In this study, we systematically investigated the formation and evolution of the chemical short-range order (CSRO) in an equiatomic CoNiV alloy using hybrid Monte Carlo/molecular dynamics simulations, with particular emphasis on the CSRO extending beyond the first and second nearest neighbors. Our results revealed a distinctive transition from $\mathrm{D}{0}_{22}$-like to $\mathrm{L}{1}_2$-like structures upon CSRO formation at intermediate temperatures. The development of CSRO significantly increases the stacking fault energy and, concomitantly, reduces the stacking fault width. Quantitatively, a linear relationship between the average degree of CSRO and stacking fault energy is established. Furthermore, repeated dislocation slips progressively disrupt CSRO and influence both the complex stacking fault energies and antiphase boundary energies. Our work provides atomistic insights into the interplay between CSRO and fault energies that govern deformation mechanisms in a model system, CoNiV, thereby offering a theoretical foundation for the process design and optimization of advanced multicomponent alloys.

Nitrogen vacancies (${\mathrm{V}}_{\mathrm{N}}$) are critical defects that influence the performance of wurtzite scandium-doped aluminum nitride ($\mathrm{A}{\mathrm{l}}_{1-x}\mathrm{S}{\mathrm{c}}_x\mathrm{N}$) ferroelectric devices. However, the microscopic mechanisms through which these vacancies influence leakage and breakdown behaviors remain insufficiently understood. Here, we investigate the formation energetics of ${\mathrm{V}}_{\mathrm{N}}$ in $\mathrm{A}{\mathrm{l}}_{1-x}\mathrm{S}{\mathrm{c}}_x\mathrm{N}$ using first-principles calculations guided by coordination-dependent defect stability principles and employing defect-tuned supercell models. Our results demonstrate that Sc-N bonds significantly lower the formation energies of ${\mathrm{V}}_{\mathrm{N}}$, with diminishing returns beyond two Sc coordination. Additionally, the spatial distribution of Sc plays a crucial role in the formation of conductive paths for ${\mathrm{V}}_{\mathrm{N}}$, suggesting that optimizing the Sc distribution can effectively suppress leakage current and delay breakdown. These insights advance the understanding of defect-driven challenges in $\mathrm{A}{\mathrm{l}}_{1-x}\mathrm{S}{\mathrm{c}}_x\mathrm{N}$ and open avenues for improving device reliability through defect engineering strategies.

We investigate how the spectral and topological properties of electron systems evolve on a lattice that interpolates between the honeycomb and its 1/6-depleted structures through the introduction of selective random defects. We find that in certain parameter regimes, the topological properties of the two lattice systems are smoothly connected, whereas in other regimes, selective random defects induce a topological transition. Analysis based on an effective model reveals that the effect of selective random defects can be understood as a modulation of hopping amplitudes. Our results highlight the potential for designing and controlling the spectral and even topological properties of electronic systems across a wide range of material platforms.

We study the dynamics of Loschmidt echoes in noisy quantum many-body systems without conservation laws. We first show that the operator Loschmidt echo in noisy unitary dynamics is equivalent to the operator norm of the corresponding dissipative dynamics upon noise averaging. We then analyze this quantity in two complementary ways, revealing universal dynamical behavior. First, we develop a heuristic picture for generic Floquet systems that connects Loschmidt echoes, out-of-time-order correlators, and operator growth, which is valid at any dissipation strength. We assert that the Loschmidt echo has two dynamical regimes depending on the time $t$ and the strength of the noise $p$: Gaussian decay for $pt\ll 1$ and exponential decay (with a noise-independent decay rate) for $pt\gg 1$. Lastly, we rigorously prove all our results for a solvable chaotic many-body quantum circuit, the dissipative random phase model—thus providing exact insight into dissipative quantum chaos.

A detailed study of the structural and magnetic properties of a spin-$5/2$ triangular lattice antiferromagnet $\mathrm{RbFe}{\left({\mathrm{HPO}}_3\right)}_2$ is presented using x-ray diffraction, magnetization, heat capacity, and ${}^{31}\mathrm{P}$ nuclear magnetic resonance (NMR) experiments on a polycrystalline sample. The crystal structure features an equilateral triangular lattice of ${\mathrm{Fe}}^{3+}$ ions. The thermodynamic measurements reveal the onset of a magnetic long-range order at $T_{\mathrm{N}1}\simeq 7.8\mathrm{K}$ in zero field, followed by another low-temperature field-induced ordering at $T_{\mathrm{N}2}$ in higher fields. The transition at $T_{\mathrm{N}1}$ is further confirmed from the NMR spin lattice relaxation measurements. The value of the frustration ratio ($f\simeq 7$) implies moderate spin frustration in the compound. The ${}^{31}\mathrm{P}$ NMR spectra exhibit two distinct spectral lines corresponding to two inequivalent phosphorus sites (P1 and P2), consistent with the crystal structure. The P1 site is strongly coupled with an isotropic hyperfine coupling of $A_{\mathrm{hf}}^{\mathrm{iso}}=0.55\left(2\right)\mathrm{T}/{\mu }_{\mathrm{B}}$ while the P2 site is weakly coupled with $A_{\mathrm{hf}}^{\mathrm{iso}}=0.25\left(3\right)\mathrm{T}/{\mu }_{\mathrm{B}}$ with the ${\mathrm{Fe}}^{3+}$ ions. The magnetic susceptibility and NMR shift data are described well assuming a spin-$5/2$ isotropic triangular lattice antiferromagnetic model with an average exchange coupling of $J/k_{\mathrm{B}}=2.8\left(2\right)\mathrm{K}$. Below $T_{\mathrm{N}1}$, the spectra evolve into a nearly rectangular powder pattern, indicating a commensurate antiferromagnetic type order. The ${}^{31}\mathrm{P}$ spin-lattice relaxation rate well below $T_{\mathrm{N}1}$ follows a $T^3$ temperature dependence, implying a two-magnon Raman scattering mechanism in the ordered state. Three well-defined phase regimes are clearly ascertained in the $H\text{−}T$ phase diagram, reflecting a weak magnetic anisotropy in the compound.

We study photon-mediated interaction between two macrospins subjected to a static magnetic induction and undergoing Larmor precession. In free space, the macrospin-macrospin interaction is reciprocal. The cooperative frequency shift and decay rate are oscillatory decaying functions of the distance of macrospins, when the retardation effect is significant. This sign-changing photon-mediated interaction of macrospins is reminiscent of the electron-mediated Ruderman-Kittel-Kasuya-Yosida interaction between magnetic impurities in metals. Inside a metallic waveguide, however, the photon-mediated interaction can become nonreciprocal. This phenomenon arises from the chiral coupling between the transverse electric (TE) modes of the waveguide and the precessing macrospins. By tuning the Larmor frequency and thereby controlling the impact of the lowest TE modes, the external magnetic induction determines the reciprocal or nonreciprocal nature of the interaction. Furthermore, optimally positioning of the macrospins within the waveguide enhances the nonreciprocal effect.

The recent discovery of high-$T_c$ superconductivity in pressurized and thin film nickelates is nowadays one of the most relevant and active topics in solid-state physics. The origin of superconductivity together with the relevance of multiorbital physics are highly discussed issues in this field. Knowledge of the size of the gap and its symmetry is of fundamental interest to uncover the superconducting mechanism at play in the nickelates. Electronic Raman scattering is a powerful tool to investigate the main characteristics of the gap. Here, we investigate the Raman response in the superconducting phase for three different models: Two-orbital models, including $d_{x^2-y^2}$ and $d_{z^2}$ orbitals, with one and two layers; as well as a bilayer model with the $d_{x^2-y^2}$ orbital as the only active one. For each of these models, we consider different pairing symmetries and determine their characteristic fingerprints in the Raman response. For the two-orbital models, we perform full multiorbital calculations including interorbital and intraorbital scattering, and compare the results with those obtained using the additive Raman response where each band is considered separately. Our results should be useful for discussing the minimal model for superconductivity and its pairing symmetry in nickelates. The obtained results and discussions, as well as the presented formalism, are also of general interest for other multiorbital systems.

We present numerical evidence that Kelvin waves (KWs) on quantized vortices in superfluid helium can be directly observed in the normal fluid component at finite temperatures. Using the fully coupled local model of superfluid turbulence (FOUCAULT) model, we analyze the propagation and temperature dependence of KWs by simultaneously measuring the dispersion of waves on the vortex displacement and the normal fluid velocity. The results demonstrate that the normal fluid supports a coherent KW-like response, with a dispersion relation matching that of the vortex filament (VF). Unlike the Schwarz model where there is almost no temperature dependence, in FOUCAULT, KWs frequency and damping both depend on temperature, highlighting the role of mutual friction in mediating the coupling between the two fluids. These findings open a pathway for experimental observation of KWs in the normal phase using tracer based visualization.

To elucidate the interplay among valence, orbitals, spin, and electronic structure in the mixed-valence compound ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_6$, we systematically investigate the electronic structure and magnetic properties using density functional theory (DFT) and DFT+dynamical mean-field theory ($\mathrm{DFT}+\mathrm{DMFT}$) methods. We tune the valence by holes and electrons doped ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_6$. Our results demonstrate that hole doping via Sr substitution on the La site with ${\mathrm{Ni}}^{2+}$ induced the metal-insulator transition. But both K substitution (hole doping) and electron doping retain metallic behaviors. For the magnetic orders, our results show that ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_6$ has the C-type antiferromagnetic (CAFM, stripe order) ground state, with a gap of 88 meV, which is in agreement with the experimental value of 54–100 meV. Our results also observe strong electronic renormalization in both the Ni-$d_{z^2}$ and Ni-$d_{x^2-y^2}$ orbitals of ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_6$, similar to the electronic correlation reported in ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$. Tuning the Coulomb interaction shows the spin and charge instabilities in ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_6$, which is consistent with the behavior of ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$.

Aliovalent rare-earth doping of ferroelectric oxides offers a route toward multifunctionality, yet its microscopic consequences remain poorly understood. Here we present a unified first-principles and crystal-field study of ${\mathrm{Gd}}^{3+}$-doped ${\mathrm{PbTiO}}_3$, combining $\mathrm{DFT}+U$ and TB-mBJ electronic structure calculations with Wannier-based crystal-field extraction, superposition modeling, Berry-phase polarization, and finite-temperature statistical mechanics. We resolve a long-standing discrepancy between prior theoretical predictions of metallicity and experimental observations of insulating behavior by demonstrating that uncompensated Gd substitution is intrinsically unstable, whereas charge compensation via Pb or O vacancies restores finite band gaps and stabilizes the ferroic lattice. Two charge-neutral configurations, ${\mathrm{Pb}}_{0.8125}{\mathrm{Gd}}_{0.125}{\mathrm{TiO}}_3$ and ${\mathrm{PbTi}}_{0.875}{\mathrm{Gd}}_{0.125}{\mathrm{O}}_{2.9375}$, are shown to be thermodynamically stable, exhibiting near-pristine spontaneous polarizations ($\left|\mathrm{\Delta }P\right|\approx 82-84\mu \mathrm{C}/{\mathrm{cm}}^2$) and robust localized $4f^7$ moments ($\sim 7{\mu }_B$). Symmetry analysis clarifies why macroscopic ferroelectricity survives strong local site symmetry breaking: the global ${\mathrm{\Gamma }}_{15}\to A_1$ polar mode remains symmetry-allowed, while defects primarily modulate local distortion amplitudes. Crystal-field theory reveals pronounced single-ion anisotropy induced by vacancy-driven symmetry reduction, whereas intersite exchange remains ultraweak ($J\sim {10}^{-3}\mathrm{meV}$) due to the spherical $4f^7$ configuration and unfavorable superexchange geometry, precluding magnetic order at accessible temperatures. Thermal disorder of the Gd moments is shown to induce an exchange-driven optical-gap redshift of $\sim 0.2-0.4\mathrm{eV}$, linking magnetism and optics without compromising ferroelectricity. These results establish charge compensation as the organizing principle governing structure, ferroic order, and electronic response in rare-earth–doped ${\mathrm{PbTiO}}_3$, and provide a transferable framework for defect-engineered multifunctional perovskites beyond conventional multiferroic paradigms.

Topological phases are expected to carry enhanced computational power, stemming from the long-range entanglement that characterizes them. Here we investigate whether this advantage is reflected in quantum nonstabilizerness (often called magic), quantified through stabilizer Rényi entropies. We analyze both integrable and nonintegrable one-dimensional models with an exact duality between a symmetry-protected topological phase and a trivial one. Surprisingly, a finite (parameter-dependent) asymmetry appears only when boundary conditions break the duality, and emerges as well in the transverse-field Ising chain, which is topologically trivial. These results complement recent analysis in the literature and show that the total of a state is unable to detect symmetry-protected topological phases, indicating either that a different property is required to capture their unique quantum contribution or that not all forms of long-range entanglement constitute a genuine computational resource.

We propose a single-layer tensor network framework for the variational determination of ground states in two-dimensional quantum lattice models. By combining the nested tensor network method [Z. Y. Xie et al., Phys. Rev. B 96, 045128 (2017)] with the automatic differentiation technique, our approach can reduce the computational cost by three orders of magnitude in bond dimension, and therefore enables highly efficient variational ground-state calculations. We demonstrate the capability of this framework through two quantum spin models: the antiferromagnetic Heisenberg model on a square lattice and the frustrated Shastry-Sutherland model. Even without GPU acceleration or symmetry implementation, we have achieved a bond dimension of nine and obtained accurate ground-state energy and consistent order parameters compared to prior studies. In particular, we confirm the existence of an intermediate empty-plaquette valence bond solid ground state in the Shastry-Sutherland model. We have further discussed the convergence of the algorithm and its potential improvements. Our work provides a promising route for large-scale tensor network calculations of two-dimensional quantum systems.

We experimentally investigate the influence of Coulomb interactions on current noise in a Fabry-Pérot cavity formed by two series-coupled quantum point contacts and a pair of side gates. By varying the side-gate voltage to tune the interaction strength, we observe pronounced deviations from the noninteracting Fano factor of 1/4. These deviations manifest as a notable noise enhancement and the emergence of positive current correlations. Moreover, in the strong interaction regime, the Fano factor exhibits a rapid increase, indicating a significant enhancement of correlation effects. Our findings are consistent with the interpretation that the measured noise characteristics are primarily attributed to interaction-modified scattering processes within the cavity.