External stimuli offer a route to realize exotic states with nontrivial excitations in highly frustrated kagome antiferromagnets. Here, 1.5% ${\mathrm{Gd}}^{3+}$ ions are substituted for ${\mathrm{Y}}^{3+}$ ions in ${\mathrm{YCu}}_3$(OD)${}_{6.5}{\mathrm{Br}}_{2.5}$ (abbreviated as ${\mathrm{YCu}}_3$), yielding ${\mathrm{Gd}}_{0.015}{\mathrm{Y}}_{0.985}{\mathrm{Cu}}_3$(OD)${}_{6.5}{\mathrm{Br}}_{2.5}$, where the ${\mathrm{Gd}}^{3+}$ ions act as a local probe to investigate fractionalized excitations in the $S=1/2$ kagome Heisenberg antiferromagnet ${\mathrm{YCu}}_3$. The Gd substitution level is confirmed through detailed x-ray diffraction analyses, while magnetization and magnetic-susceptibility measurements disclose the interaction between the substituted Gd ions and the Cu-spin kagome network. Specific-heat measurements in magnetic fields up to 14 T and down to dilution-refrigerator temperatures reveal an enhanced density of low-energy states, indicative of spinon-impurity coupling, yet higher-energy excitations are hardly affected. Furthermore, high-frequency electron spin resonance (ESR) measurements, enabled by the presence of Gd as a local probe, present the resonance associated with Gd ions coupled with the kagome spins. In particular, the temperature dependence of the ESR linewidth exhibits a near-quadratic power-law behavior, revealing the presence of Dirac spinon dynamics in the finite-temperature regime above 2 K.

It has been shown that oxides containing multiple transition elements with near equi-atomic compositions have a strong tendency to crystallize into a single phase via configurational entropy. In this regard, we have synthesized and stabilized a new composition $\left(\mathrm{M}{\mathrm{n}}_{0.25}\mathrm{C}{\mathrm{o}}_{0.25}\mathrm{N}{\mathrm{i}}_{0.25}\mathrm{M}{\mathrm{g}}_{0.25}\right)\mathrm{F}{\mathrm{e}}_2{\mathrm{O}}_4$ in nano- and bulk forms via chemical co-precipitation and standard solid-state reaction methods, respectively. The crystal structures of the synthesized samples crystallize in a pure spinel phase as confirmed by x-ray diffraction patterns. We have adopted different characterization techniques to investigate the structural, magnetic, and optical properties of samples prepared by different routes. We have investigated their dynamical behavior extensively by performing ac susceptibility measurements under different ac frequencies, magnetic memory effect in the negative and positive cycles under different temperatures and fields, thermoremanent magnetization, and aging effect. We have analyzed and fitted the frequency dependence of the freezing temperature using empirical laws, namely the Néel-Arrhenius law, the Vogel-Fulcher law, and the power law. The sample prepared by the coprecipitation technique exhibits a cluster spin-glass-like state as realized from the Mydosh parameter, relaxation time, and critical exponent. In contrast, this behavior is absent in the sample prepared by the solid-state reaction method. Furthermore, we have investigated the magnetic memory effect in the annealed samples and found that the nanosized samples exhibit a pronounced memory effect, which typically weakens as particle size increases towards the bulk regime. The obtained results of the memory effect are consistent with a hierarchical model of spin-glass. We have been able to determine the correct ground state for the inverse spinel structure using GGA+$U$ and hybrid exchange-correlation functionals, which agrees well with our experimental outcomes. Further, we have correlated our theoretical results from some spectroscopic measurements such as x-ray photoelectron spectroscopy, UV-Visible-NIR spectroscopy, and ultraviolet photoelectron spectroscopy. Our combined experimental and theoretical study provides new insights that significantly broaden the understanding of entropy-stabilized spinels and their applications in the field of magnetic storage.

A phase field simulation framework is used to study the martensitic microstructure and mechanical behavior of lath martensite. The model takes into account all 24 martensite variants of steel and also considers the hierarchical microstructure at the level of packets and blocks. Elastic and plastic effects are incorporated into the model. Particular emphasis is given to understand the effect of plasticity associated with martensite variant interfaces. A model parameter that can control the yielding behavior of the interfaces is introduced. It is shown that the extent of interfacial yielding can significantly influence the observed martensite morphology. The evolution of the lath martensite microstructure under loading is also simulated for different interfacial yielding conditions. It is shown that, in principle, there are two mechanisms by which the applied load can be accommodated. The first is the plastic deformation associated with the variant interfaces and the second is the growth/shrinkage of favored/unfavored variants. It is shown that these are competing mechanisms. When the interfacial plasticity is significant, the variant growth/shrinkage mechanism is suppressed.

This paper presents results of atomistic simulations under high pressures and temperatures for platinum. To obtain precise models of interatomic interactions, machine learning potentials are fitted for a set of isotherms in the temperature range of 2–70 kK. Training sets are prepared from snapshots extracted from ab initio molecular dynamics trajectories calculated in the framework of density functional theory taking into account not only the vibrational degrees of freedom of ions but also the excitation of the electronic subsystem. The latter means that it is necessary to derive the potential for each particular temperature. Trained interatomic potentials give an accuracy better than 5 meV/atom in comparison with the results of ab initio calculations. Calculations of structural and transport properties are performed in the temperature range of 2–70 kK. Shear viscosity, self-diffusion coefficients, the Stokes-Einstein relation, and the pair correlation function are obtained. Calculations show the significance of many-body interactions in the platinum liquid phase. The high-pressure and -temperature phase diagram of platinum is determined with the thermodynamic integration technique and compared with existing experimental data and other theoretical predictions. The current evaluation of the phase diagram excludes any crystal structures in the considered pressure-temperature range other than the fcc.

Disorder-free quantum many-body localization can strongly suppress transport while still enabling the dynamical buildup of computationally costly non-Clifford resources. In a tilted transverse-field Ising chain realizing disorder-free Stark many-body localization, we use the stabilizer Rényi entropy to quantify quantum magic (nonstabilizerness) and find that it remains finite and grows anomalously slowly over extended time windows before saturating to a size-dependent plateau deep in the strong-tilt regime, with pronounced initial-state selectivity. Upon increasing the Stark gradient, the long-time magic and half-chain entanglement exhibit consistent finite-size crossing behavior, indicating a crossover from ergodic dynamics to constrained localization. These results establish stabilizer-based magic as a practical complexity diagnostic of disorder-free ergodicity breaking and constrained dynamics, and provide an experimentally accessible route to benchmarking and designing near-term quantum simulators.

The magnetic structure of ${\mathrm{Hg}}_{0.7}{\mathrm{Na}}_{0.3}{\mathrm{Mn}}_3{\mathrm{Mn}}_4{\mathrm{O}}_{12}$, a quadruple manganite perovskite that exhibits a unique $G$-type charge- and orbital-ordered state distinct to other $A^{2+}{\mathrm{Mn}}_3{\mathrm{Mn}}_4{\mathrm{O}}_{12}$ equivalents $(A=\mathrm{Ca},\mathrm{Sr},\mathrm{Cd},\mathrm{Pb})$, has been solved using powder neutron diffraction and symmetry-motivated analysis. A $G$-type-like antiferromagnetic (AFM) ordering of Mn on the $A^{\prime }$ sites and a ‘‘up-up–down-down’’ AFM moment configuration of Mn spins on the $B$ sites is found to occur. The mechanism for the onset and stabilization of $B$-site up-up–down-down AFM order is explored in terms of coupling between structural and magnetic distortions. The results presented here provide evidence of the exotic charge, orbital, electronic, and magnetic orderings that quadruple manganite perovskites demonstrate, and further highlighting the distinct chemistry that ${\mathrm{Hg}}^{2+}$ plays in stabilizing novel states compared to other divalent $A$-site cation equivalents.

We revise the quantum hydrodynamics of superfluids to account for the refraction of matter waves. Provided that the density fluctuations are small, the refraction may be incorporated into the low-energy theory by renormalization of the bare particle mass. We analytically demonstrate the consistency of the approach on a model system of hard spheres. At short wavelengths, the elementary excitation spectrum connects with the Beliaev expression featuring the roton minimum. Consecutive autolocalization of rotons and phonons at elevated densities results in a dramatic modification of the static structure factor as compared to the Bogoliubov theory: its shape approaches that characteristic of the random close packing. The isothermal compressibility diverges, signaling a first-order quantum phase transition. At moderate densities refraction stabilizes the Bose-Einstein condensate while reducing the superfluid fraction.

Frustrated Kondo lattices are ideal platforms for studying how both the Kondo effect and quantum fluctuations compete with the magnetic exchange interactions that drive magnetic ordering. Here, we investigate the effect of tuning the heavy-fermion compound CePdIn, which crystallizes in the geometrically frustrated ZrNiAl-type structure, using applied magnetic fields and hydrostatic pressure. At ambient pressure, CePdIn exhibits two magnetic transitions, one at $T_{\mathrm{N}}\approx 1.65\mathrm{K}$ and another at $T_{\mathrm{M}}\approx 1.15\mathrm{K}$, which are both suppressed by applied $c$-axis fields. Upon applying pressure in zero magnetic field, there is a nonmonotonic evolution of $T_{\mathrm{N}}$, which decreases to 0.8 K at 2.3 GPa, before abruptly increasing to 1.5 K at 2.6 GPa. At higher pressures, $T_{\mathrm{N}}$ has a weak pressure dependence and vanishes near 5 GPa. Together with the high-pressure phase being more robust to applied fields, these results suggest two distinct antiferromagnetic phases in CePdIn, which are separated near 2.6 GPa, and this change may be driven by the evolution of the underlying electronic structure due to enhanced Kondo hybridization under pressure.

Quantum emitters inside optical cavities can create not only fixed photon number states but also photon number wave packets, which are states with a finite photon number distribution that oscillates in time. These states emerge when the emitter is driven by an external field while coupled to the cavity. We show that by rapidly changing the driving strength, new wave packets can be generated, allowing multiple packets to coexist and evolve independently. We classify the resulting wave packet behavior into distinct dynamical subclasses between which we choose through the choice of relevant parameters. Based on this understanding, we develop simple and robust protocols to generate a specified number of photon number wave packets on demand. We propose that the rich dynamics can be experimentally investigated by merely measuring the mean photon number.

We study the effects of dissipation in the phase diagram of the random quantum Ashkin-Teller model by means of a generalization of the strong-disorder renormalization group combined with adiabatic renormalization. This model has three phases and three quantum phase transitions. We demonstrate that the combined effect of Ohmic dissipation and quenched disorder smears two out of the three quantum phase transitions. Our analytical theory allows us to understand why one of the phase transitions remains sharp. This is due to a cancellation of the dissipation effects on the nontrivial nature of the intertwined order parameter of one of the phases.

Frequent interventions on an open quantum system can suppress or enhance decay, giving rise to quantum Zeno and anti-Zeno effects, but their impact on coherent transport in extended systems remains less explored. Motivated by continuous resetting protocols in quadratic open systems, we develop a microscopic theory of reset-controlled transport through a tight-binding chain with a bright/dark lossy region coupled to a structured reservoir. Starting from a repeated-interaction model, we derive a Kofman-Kurizki-type decay rate whose dependence on the reset interval is governed by a sinc-squared filter. For smooth Ohmic baths this produces a purely Zeno-like suppression of transport, whereas for Lorentzian structured baths it yields a pronounced Zeno–anti-Zeno crossover that is reflected in the transmission of a single bright/dark dimer and in the exponential attenuation of chains of many dimers. We map out energy- and length-resolved transport phase diagrams, extend the resetting protocol to finite-temperature reservoirs, and analyze charge and heat currents within a Landauer framework. Finally, by periodically repeating the bright/dark cell we construct a reset-controlled non-Hermitian lattice whose complex Bloch bands host exceptional points (EP) tuned by the reset interval; the corresponding EP time coincides with the strongest suppression of transport, establishing a direct link between resetting protocols, Kofman-Kurizki dynamical control, and non-Hermitian band engineering in mesoscopic quantum transport.

We study theoretically the nonlinear optical response of twisted AA- and AB-stacked bilayer graphene quantum dots placed in the field of an ultrashort optical pulse. We consider the cases of both linearly and circularly polarized pulses, and we characterize the nonlinear optical response of the system in terms of nonlinear absorption and high harmonic generation. The low-energy states of a bilayer quantum dot system are mainly localized at the quantum dot edges. As a result, such states and correspondingly the nonlinear optical response become very sensitive to the twist angle. In general, the nonlinear optical response of twisted bilayer quantum dots is enhanced when a finite twist angle is introduced. The nonlinear optical absorptance as a function of the twist angle shows a strongly nonmonotonic dependence with the maxima that are realized at a finite angle, with the maximum values that are a few times larger than the absorptance of the untwisted bilayer system. The dependence of the absorptance on the twist angle is partially correlated with the profile of a quantum dot band gap as a function of the angle. The high harmonic generation in twisted bilayer quantum dots shows a very strong sensitivity to the twist angle, especially for large-order harmonics and small quantum dots consisting of 142 atoms. For small-order harmonics, the intensities of the harmonics as a function of the twist angle show nonmonotonic oscillatory behavior with the intensities that change by a few orders of magnitude. For a circularly polarized pulse, some high-order harmonics are strongly suppressed for untwisted quantum dots due to $C_3$ rotational and inversion symmetries, where the inversion symmetry is present only in an AB-stacked untwisted system. These harmonics are strongly enhanced when a finite twist angle is introduced.

We report muon-spin relaxation (${\mu }^{+}\mathrm{SR}$) measurements of copper acetate [$\mathrm{Cu}{\left({\mathrm{CH}}_3{\mathrm{CO}}_2\right)}_2·{\mathrm{H}}_2\mathrm{O}$], a model spin-1/2 Heisenberg antiferromagnetic dimer chain with an alternation parameter $\alpha$ = 0.001. Zero-field ${\mu }^{+}\mathrm{SR}$ data collected from 2 to 200 K revealed an oscillatory asymmetry that was analyzed using a model based on the muon-stopping site determined by density-functional theory $+\mu$ calculations. Below 50 K, the fitted parameters capture spin dynamics characteristic of the singlet ground state, while at higher temperatures, an additional relaxation was observed due to the thermally populated triplet state, affecting the local magnetic field around the muon-stopping site. The temperature dependence of the fitting parameters was found to exhibit characteristics similar to those of a bipartite entanglement measure, “distance between the states,” obtained from the magnetic susceptibility data. Longitudinal-field ${\mu }^{+}\mathrm{SR}$ measurements reveal field-dependent relaxation at field values much lower than the field values required to close the spin singlet-triplet gap, emphasizing the importance of quantum fluctuations in the spin dynamics of the dimerized copper acetate.

Rydberg atom quantum simulator platforms are novel quantum simulators for physical systems ranging from condensed matter to particle physics. In this paper, we study out-of-equilibrium quantum dynamics in a model of Rydberg atoms arranged in ladder geometries, with a semistaggered detuning profile. As the staggering strength ($\mathrm{\Delta })$ is varied from $0\to \infty$, the model exhibits a wide class of dynamical phenomena, ranging from quantum many-body scars ($\mathrm{\Delta }\sim 0,1$) to integrability induced slow dynamics and approximate Krylov fractures ($\mathrm{\Delta }\ge 2$). We study the robustness of these dynamical features against inevitable influences from the environment in the form of pure dephasing and the finite lifetime of the Rydberg excited state. Additionally, by leveraging an underlying spectral reflection symmetry, we design Floquet protocols having dynamical signatures reminiscent of discrete-time-crystalline order and exact Floquet flat bands, and study their stability under protocol imperfections. Finally, we consider long-range van der Waals interactions and investigate the validity of the kinetic constraints in an out-of-equilibrium scenario.

In this paper we theoretically discuss thermal Hall effect of magnons in insulating Néel ordered antiferromagnets at zero external magnetic field. We show that for compensated Néel order the nonzero thermal Hall effect will occur in the absence of any symmetry between the two magnetic sublattices, thus making the system ferrimagnetic. We then show that collinear Dzyaloshinskii's weak ferromagnets, in which there is a symmetry connecting the magnetic sublattices, also show magnon thermal Hall effect. The thermal Hall effect of magnons will be nonzero by a virtue of the spin-momentum splitting of the magnon spectrum due to the Dzyaloshinskii-Moriya interaction as well as second-nearest exchange interaction different in the two magnetic sublattices, both corresponding to the broken symmetries that lead to the Dzyaloshinskii's invariant. We construct a theoretical model in which an external electric field may change the symmetry of the antiferromagnetic system thus altering the thermal Hall effect of magnons.

The tunability of anomalous Hall and Nernst conductivities is investigated in the compensated ferrimagnet ${\mathrm{Mn}}_3\mathrm{Al}$ under isotropic strain $\left(\eta \right)$ and chemical potential variation using first-principles calculations. At a chemical potential of $\mu =-0.3\mathrm{eV}$, three distinct topological features—Weyl points, nodal lines, and gapped nodal lines—are simultaneously realized along high-symmetry directions of the Brillouin zone in the framework of magnetic space groups. The anomalous Hall conductivity is found to be predominantly governed by the Berry curvature in the $k_y{k}_z$ plane and can be enhanced significantly under tensile strain, reaching $-1200$ ${\left(\mathrm{\Omega }\mathrm{cm}\right)}^{-1}$. On the other hand, the anomalous Nernst conductivity shows a sign change near the Fermi level and whose magnitude increases at $\mu =-0.3\mathrm{eV}$ with quasiquadratic strain dependence. Regardless of strain, the underlying bands and Fermi-surface structures remain robust, while the distribution and magnitude of Berry curvature evolve substantially. These results underscore the potential of ${\mathrm{Mn}}_3\mathrm{Al}$, a compensated ferrimagnet, as a platform for Berry curvature engineering via strain and doping.

The magnetocaloric effect (MCE) is an inherent characteristic of magnetic materials and is considered a potential mechanism for environmentally friendly magnetic refrigeration. However, research on the MCE has been long absent within the field of two-dimensional (2D) magnets. By employing Landau theory of phase transitions, first-principles calculations, and Monte Carlo simulations, we have demonstrated that the transition from bulk to 2D will reduces the MCE in ${\mathrm{Fe}}_3{\mathrm{GeTe}}_2$ (FGT). Remarkably, the MCE performance of the FGT monolayer can be significantly enhanced through substrate engineering. When 2D FGT is placed on InP(111) and Pb(111) substrates, the maximum $-\mathrm{\Delta }{S}_{\mathrm{m}}$ increases from $3.75\mathrm{J}\mathrm{K}{\mathrm{g}}^{-1}{\mathrm{K}}^{-1}$ to 9.9 and $17.4\mathrm{J}\mathrm{K}{\mathrm{g}}^{-1}{\mathrm{K}}^{-1}$, and the corresponding maximum relative cooling power increases from $150.0\mathrm{J}\mathrm{K}{\mathrm{g}}^{-1}$ to 996 and $3742\mathrm{J}\mathrm{K}{\mathrm{g}}^{-1}$ under an out-of-plane magnetic field of 9 T. These enhancements originate from interfacial charge transfer between FGT and the substrates, which improves the MCE performance by simultaneously optimizing magnetic anisotropy energy and interlayer magnetic coupling strength ($J_1$ and $J_2$). These findings provide a deeper understanding of the dimensionality effect on MCE and identify FGT heterojunctions as promising materials for low-dimensional magnetic refrigeration applications.