The appearance of broken time-reversal symmetry (TRS) in superconducting states is an intriguing issue in solid-state physics because of the incompatibility of the spontaneous magnetic field and the Meissner effect. We identify broken TRS in Pd-doped CaAgP (${\mathrm{CaAg}}_{0.9}{\mathrm{Pd}}_{0.1}\mathrm{P}$) by point-contact spectroscpy through the magnetic-field response of conductance spectra. ${\mathrm{CaAg}}_{0.9}{\mathrm{Pd}}_{0.1}\mathrm{P}$ is a nodal-line semi-metal with exotic electronic states such as drumhead surface states and surface superconductivity. Tunneling conductance spectra acquired at the side surfaces of ${\mathrm{CaAg}}_{0.9}{\mathrm{Pd}}_{0.1}\mathrm{P}$ under an applied magnetic field exhibit broad zero-bias peaks with small asymmetric structures. Surprisingly, the asymmetric structures are reversed exactly by flipping the field direction. On the basis of an analysis which stands on the formula of tunneling junctions for unconventional superconductors, these results are consistent with the pair potential of the superconductivity breaks with the TRS and is strongly coupled to an external magnetic field. We reveal the novel character of superconducting nodal-line semi-metals by developing the TRS sensitivity of point-contact spectroscopy. Our results serve as an exploration of broken TRS in superconducting states realized in topological materials.

A series of experiments revealed that novel bipartite magnetic and superconducting (SC) phases widely exist in the phase diagrams of iron pnictides and chalcogenides. Nevertheless, the origin of the two-dome magnetic and SC phases in iron-based compounds remains unclear. Here we theoretically investigated the electronic structures, magnetic, and SC properties of three representative iron-based systems, i.e., ${\mathrm{LaFeAsO}}_{1-x}{\mathrm{H}}_x, {\mathrm{LaFeAs}}_{1-x}{\mathrm{P}}_x\mathrm{O}$, and ${\mathrm{KFe}}_2{\mathrm{As}}_2$. We propose a unified quasidegenerate orbital mechanism for the emergence of the two-dome parent magnetic/structural phase and the subsequent two-dome SC phase. It is found that the degenerate in-plane anisotropic $d_{xz/yz}$ orbitals dominate the first magnetic/structural and SC phases, while in-plane isotropic orbitals $d_{xy}$ or $d_{3z^2-r^2}$ with quasidegeneracy originating from quasisymmetry drive the emergence of the second magnetic/SC dome phase. Moreover, a matching rule of spin and orbital modes for SC pairing state is proposed in multiorbital iron-based systems. These results imply an orbital-driven mechanism as well as an orbital-selective scenario and shed light on the understanding of the multidome magnetic and SC phases in multiorbital systems.

Given that ${\mathrm{Al}}_2{\mathrm{O}}_3$ (alumina) is a primary component of silicate magmas in deep planetary interiors, elucidating the structural transformations of amorphous alumina ($a\text{−}{\mathrm{Al}}_2{\mathrm{O}}_3$) under extreme pressures is crucial for understanding the evolution and dynamics of deep silicate magmas. However, the extremely low glass-forming ability of alumina has made it technically difficult to synthesize sufficient quantities of pure $a\text{−}{\mathrm{Al}}_2{\mathrm{O}}_3$ for measurement. Structural information has thus been largely confined to amorphous nanofilms at ambient pressure, limiting our understanding of structural transformations under ultrahigh-pressure conditions. Here, we have employed recently established pulsed-laser deposition techniques to synthesize high-quality, millimeter-sized $a\text{−}{\mathrm{Al}}_2{\mathrm{O}}_3$, which enabled us to conduct in situ Brillouin scattering spectroscopic measurements in a diamond anvil cell, measuring acoustic velocities under pressures up to 174 GPa. The results reveal two distinct pressure regimes in transverse acoustic velocity: (i) a monotonic increase up to $\sim 120$ GPa, and (ii) a steep increase above $\sim 120$ GPa. These behaviors mirror those observed in $\mathrm{MgSi}{\mathrm{O}}_3$ glass and can be interpreted as (i) a transition from $4^{++}$ to 6-fold Al-O coordination, and (ii) the emergence of coordination states beyond 6-fold. The experimental observation of $6^{+}$ coordination under extreme pressure provides novel insights into the densification mechanisms of $a\text{−}{\mathrm{Al}}_2{\mathrm{O}}_3$ and silicate melts within terrestrial planet interiors, offering essential constraints on the dynamics and evolution of deep magma oceans during early planetary formation.

Polarons are quasiparticles that arise from the coupling of electrons or holes with ionic vibrations in polarizable materials. Typically, they are either localized at a single atomic site or delocalized over multiple sites. However, after the desodiation of ${\mathrm{Na}}_2{\mathrm{Mn}}_3{\mathrm{O}}_7$, we identify a rare split-hole polaron, where a single hole is shared between two adjacent oxygen atoms rather than fully localized or delocalized. We present a density functional theory study on the migration and transport properties of these oxygen hole polarons in ${\mathrm{NaMn}}_3{\mathrm{O}}_7$ and ${\mathrm{Na}}_{1.5}{\mathrm{Mn}}_3{\mathrm{O}}_7$. Our calculations reveal that the split polaron configuration near a sodium vacancy is the ground state, while the localized polaron acts as the transition state. Migration occurs via a stepwise charge transfer mechanism along the $b$ axis, where the split-hole polaron transitions through a localized hole state. This transport behavior closely resembles the Grotthuss mechanism, which describes proton transport in ${\mathrm{H}}_2\mathrm{O}$. We compute the polaron mobility as $\mu =1.37\times {10}^{-5}$ ${\mathrm{cm}}^2$/($\mathrm{V}\mathrm{s}$) with an energy barrier of 242 meV. Using the Mulliken-Hush theory, we determine the electronic coupling parameter $V_{AB}=0.87$ eV. A similar migration mechanism is observed in ${\mathrm{Na}}_{1.5}{\mathrm{Mn}}_3{\mathrm{O}}_7$, where the split polaron remains more stable than in the localized state. This study provides a theoretical investigation of split-hole polaron migration, offering insights into the charge transport of exotic polaronic species in materials with implications for a wide range of functional materials including battery cathodes, thermoelectrics, photocatalysts, and next-generation optoelectronic devices.

We present a systematic ab initio study of the thermoelastic properties of hcp osmium as functions of temperature and pressure within the quasiharmonic approximation (QHA). The precision of the zero static internal stress approximation (ZSISA) and of the volume-constrained ZSISA (V-ZSISA) is rigorously assessed. For osmium, we find negligible deviations between ZSISA and a full free energy minimization approach. Also, the V-ZSISA approximation influences the results very little, as we found already in beryllium, despite the markedly different behavior of the $c/a$ ratio with temperature in the two metals. Our QHA-derived elastic constants (ECs) show excellent agreement with available experimental data in the temperature range of 5–301 K, outperforming the results obtained from the quasistatic approximation (QSA). Additionally, we report the pressure-dependent QHA ECs at 5, 301, and 1000 K, spanning pressures from 0 to 150 kbar.

The comprehension of quantum phase transitions (QPTs) is considered as a critical foothold in the field of many-body physics. Developing protocols to effectively identify and understand QPTs thus represents a key but challenging task for present quantum simulation experiments. Here, we establish a dynamical quench-interferometric framework to probe a zero-temperature QPT, which utilizes the evolved state by quenching the QPT Hamiltonian as input of a unitary interferometer. The metrological capability quantified by the quantum Fisher information shows a unique peak in the vicinity of the quantum critical point, allowing us to probe the QPT without cooling the system to its ground state. We show that the probing can be implemented by extracting quantum fluctuations of the interferometric generator as well as parameter estimation uncertainty of the interferometric phase and subsequently allows identifying the boundary of the phase diagram. Our results establish an important link between QPTs and quantum metrology and enrich the toolbox of studying nonequilibrium many-body physics in current quantum simulators.

In this work, we explore the robustness of a bit-flip operation against thermal and quantum noise for bits represented by the symmetry-broken pairs of the period-doubled states in a classical parametric oscillator and discrete time crystal (DTC) states in an open fully connected spin-cavity system, respectively. The bit-flip operation corresponds to switching between the two period-doubled and DTC states induced by a defect in a periodic drive. The defect is introduced in a controlled manner by linearly ramping the phase of the modulation of the drive. In the absence of stochastic noise, strong dissipation results in a more robust bit-flip operation in which slight changes to the defect parameters do not significantly lower the success rate of bit flips. The operation remains robust even in the presence of stochastic noise when the defect duration is sufficiently large. By considering parameter regimes in which the DTC states in the spin-cavity system do not directly map to the period-doubled states, we reveal that this robustness stems from the system being quenched by the defect towards a new phase that has enough excitation to suppress the effects of the stochastic noise. This allows for precise control of the bit-flip operations by tuning into the preferred intermediate state that the system will enter during a bit-flip operation. We demonstrate this in a modified protocol based on precise quenches of the driving frequency.

The generation of a single-magnon state is one of the central goals in the emerging field of quantum magnonics. Here, we propose a simple protocol to achieve this goal in anisotropic ferromagnets, where the magnons naturally form an equilibrium-squeezed vacuum state. Applying a static magnetic field to the anisotropic ferromagnet, the ferromagnet will be prepared in a squeezed coherent state due to the displacement introduced by the static magnetic field. When the amplitude of the magnetic field is properly chosen, we show that the two-magnon occupation could be zero due to destructive interference between the displacement and squeezing, leaving a large probability for occupation in the single-magnon state. This is the so-called unconventional magnon blockade. Employing the second-order correlation function to characterize the statistical property of magnons, we find the unconventional magnon blockade is robust against the system's decay. This robustness comes from the equilibrium nature of magnon squeezing. Our study provides a possible strategy for generating a stable single-magnon source.

Magnetoelectric (ME) materials face challenges in terms of practical applications and understanding of the underlying mechanisms of some phenomena. Studying these phenomena in glassy systems may provide fresh insights, but research along these lines remains limited. Our study reveals the existence of a glassy state at high temperature in single-crystal $\mathrm{FeNiM}{\mathrm{o}}_3{\mathrm{O}}_8$ (FNMO), providing a unique perspective for comprehending other high-temperature physical phenomena in this system. Remarkably, FNMO exhibits enhanced ME coupling, achieving the ME effect at elevated temperatures relative to other members of the $M_2{\mathrm{Mo}}_3{\mathrm{O}}_8$ family, and coupling with a higher second-order ME coefficient than its parent phase. Our research establishes a direct relation between the ME effect and the glassy state. The emergence of exchange bias in FNMO is controlled by the spin coupling at the interface between the glassy state and the antiferromagnetic state, opening up novel pathways for developing high-performance magnetic memories by using single-phase materials.

A class of magnetic materials known as altermagnets exhibits an emerging spin-valley locking and provides a platform for valleytronics. Unlike traditional valleytronic materials, the valley degeneracy in altermagnets is protected by crystal symmetries rather than time-reversal symmetry. It is found that the crystal symmetries linking two spin sublattices can be broken by an in-plane electric field or a magnetic field, resulting in the lifting of valley degeneracy. The magnitude of valley splitting strongly depends on the electric field, but weakly on the magnetic field. Furthermore, we combine the two physical fields to jointly modulate the valley of monolayer ${\mathrm{V}}_2{\mathrm{Se}}_2\mathrm{O}$. The results demonstrate that when the direction of the applied physical field is fixed, the magnetic field has a significant effect on valley splitting in the case of a small electric field strength. However, as the electric field strength increases, this effect significantly decreases, a consequence of the fact that the valley polarization in altermagnets is caused by exchange interactions instead of spin-orbit coupling. The findings demonstrate the potential for achieving multiphysics fields controlled valley in altermagnets.

We investigate the structural, magnetic, and thermodynamic properties of ${\mathrm{Ba}}_3{\mathrm{Sb}}_{1+x}{\mathrm{Co}}_{2-x}{\mathrm{O}}_{9-\delta } (x=0.04,\delta =0.54)$, a hexagonal perovskite featuring face-sharing ${\mathrm{CoO}}_6$ octahedra that form Co dimers. DC and AC magnetization measurements reveal a frequency-dependent spin-freezing transition consistent with glassy dynamics. AC susceptibility fits best to the Vogel-Fulcher model, indicating collective freezing of interacting spin clusters. Isothermal magnetization follows the Langevin function, suggesting finite-sized magnetic clusters rather than isolated paramagnetic moments. Nonequilibrium dynamics, evidenced by thermoremanent magnetization and memory effects, further support a spin-glass-like state. Heat capacity shows no sharp anomalies, and neutron powder diffraction confirms the absence of magnetic Bragg peaks down to 1.5 K, ruling out long-range magnetic order. Rietveld refinement reveals significant Co/Sb intersite disorder ($\sim 30\%$) and oxygen nonstoichiometry, introducing exchange randomness and frustration that drive the spin-glass-like behavior. Electrical resistivity exhibits Arrhenius-type temperature dependence with an activation energy of 0.173 eV, consistent with semiconducting behavior. Temperature-dependent x-ray diffraction shows no structural phase transitions, confirming that the spin-glass-like state is not lattice driven. Our results establish ${\mathrm{Ba}}_3{\mathrm{Sb}}_{1+x}{\mathrm{Co}}_{2-x}{\mathrm{O}}_{9-\delta }$ as a cluster spin-glass candidate, where Co dimers, disorder, and geometric frustration prevent long-range order, leading to slow spin dynamics. These findings highlight the role of cation disorder and oxygen vacancies in stabilizing unconventional magnetic states in cobalt-based hexagonal perovskites.

Lifshitz invariant is a symmetry invariant composed of multiple order parameters that contain a single spatial derivative in a Ginzburg-Landau (GL) free energy, which may induce a nonuniform configuration of the order parameters. In multiband superconductors, we find phase transitions from a uniform superconducting state to qualitatively distinct two pair-density-wave (PDW) states with small and large momenta $\mathit{q}$ based on the GL theory. The former is induced by the Lifshitz invariant, while the latter originates from the drag effect. In the PDW states, the Higgs and Leggett modes (i.e., collective amplitude and relative phase oscillations of the order parameters) are shown to couple to electromagnetic fields linearly. We construct microscopic models of multiband superconductors with Lifshitz invariant that exhibit PDW states, and calculate the linear optical conductivity using the diagrammatic approach. We find optically active Higgs and Leggett modes in the small $\mathit{q}$ PDW state, indicating that the PDW state is a suitable platform to explore collective modes of multiband superconductors in the linear response regime.

Chirality in crystals arises from the exclusive presence of proper symmetry operations, such as rotations and screw axes, while improper operations like inversion, mirror planes, and rotoinversions are absent. Crystallographic chirality is expected to be coupled with magnetic responses in magnetically active chiral compounds. Therefore, this study investigates the interplay between structural chirality and magnetic ordering in the rare-earth platinum boride family $R{\mathrm{Pt}}_2\mathrm{B}$, where $R$ denotes lanthanide elements. Our results show that the $R$ sites structurally form a chiral three-dimensional kagome lattice, which can lead to magnetic frustration resolved through chiral antiferromagnetic orderings in conjunction with chiral symmetry. Symmetry analysis reveals that these chiral antiferromagnetic states are low-energy states, competing with the higher-in-energy (001) ferromagnetic configuration. We also identified Kramers-type Weyl points in the electronic structure in the $k$ paths perpendicular to the screw axis and Weyl points along the $\mathrm{\Gamma }\text{−}A$ axis. In the magnetically active chiral compound ${\mathrm{NdPt}}_2\mathrm{B}$, Zeeman splitting lifts degeneracies at the high-symmetry points; however, Weyl points persist along the screw axis due to the breaking of time-reversal $\left(\mathcal{T}\right)$ and inversion $\left(\mathcal{P}\right)$ symmetries. We also estimate the allowed anomalous Hall conductivity, finding a value of ${\sigma }_{xy}=293\mathrm{S}{\mathrm{cm}}^{-1}$, comparable to that of known kagome magnetic materials such as ${\mathrm{Mn}}_3\mathrm{PtN}$ and FeSn. Thus, our study sheds light on the intricate interplay among chirality, magnetism, and topology in rare-earth three-dimensional kagomelike materials.

Recent magnetotransport studies on uniaxial ferromagnets have reported a cusplike feature in Hall resistivity when the magnetic field is tilted away from the conventional orthogonal direction of the Hall measurement. This feature has often been attributed to the topological Hall effect arising from a noncoplanar spin structure. In this article, we have studied the uniaxial ferromagnet ${\mathrm{SmMn}}_2{\mathrm{Ge}}_2$ to demonstrate that this feature is rather a consequence of the nonorthogonal geometry of the Hall measurement and is expected to appear whenever the magnetic field is applied away from the easy axis of magnetization, nonorthogonal to the sample plane. The Hall resistivity, exhibiting this feature, scales with the orthogonal component of the magnetization, indicating that the observed feature is simply a manifestation of the anomalous Hall effect. We explain the origin of this feature based on the evolution of ferromagnetic domains under a nonorthogonal external magnetic field.

Studying charge transport in models with nonlocal carrier–phonon interaction is difficult because it requires finite-temperature real-time correlation functions of mixed carrier–phonon operators. Focusing on models with discrete undamped phonon modes, we show that such correlation functions can be retrieved from the hierarchical equations of motion (HEOM), although phonons have been integrated out. Our procedure relies on the general explicit expression of HEOM auxiliaries in terms of phonon creation and annihilation operators. It reveals that the auxiliaries describe multiphonon-assisted carrier transitions induced by genuine many-phonon correlations, from which lower-order correlations are subtracted according to the finite-temperature Wick's theorem. Applying the procedure to our recently developed momentum-space HEOM method featuring appropriate hierarchy closing, we compute the numerically exact dynamical mobility of a carrier within the one-dimensional Peierls model. The carrier mobility at moderate temperatures decreases with increasing interaction, whereas high temperatures see the opposite trend, reflecting the prevalence of the phonon-assisted current over the purely electronic band current. The pronounced finite-size effects and HEOM instabilities delimit the range of applicability of our approach to moderate interactions, moderate to high temperatures, and not too fast phonons. Importantly, this range comprises the values relevant for charge transport in crystalline organic semiconductors, and we present and discuss the corresponding numerically exact results in a companion paper [Janković, Phys. Rev. B 112, 035112 (2025)].

Transport of charge carriers in mechanically soft semiconductors is mainly limited by their interaction with slow intermolecular phonons. Carrier motion exhibits a crossover from superdiffusive to subdiffusive, producing a distinct low-frequency peak in the dynamical-mobility profile. These features can be understood within approaches relying on the timescale separation between carrier and phonon dynamics, such as the transient localization scenario (TLS). However, recovering them from fully quantum dynamics has proved elusive. Using the hierarchical equations of motion (HEOM)-based approach exposed in a companion paper [Janković, Phys. Rev. B 112, 035111 (2025)], we study carrier transport in the one-dimensional Peierls model near the adiabatic limit. We find that the TLS approximates HEOM dynamics very well at higher temperatures and for stronger interactions. Then, the transport is predominantly phonon-assisted and turns diffusive from the subdiffusive side well before one phonon period. In contrast, the band current dominates at moderate temperatures and interactions, relevant for transport in realistic materials. We then conclude that the super-to-subdiffusive crossover is transient, so that the diffusive motion sets in from the superdiffusive side on timescales comparable to the phonon period. The low-frequency dynamical mobility then additionally exhibits a dip at approximately one phonon frequency and the zero-frequency peak. Our findings in this moderate regime show limitations of the TLS and support the results of the most advanced quantum–classical simulations. We expect that the qualitative differences between HEOM and TLS dynamics would diminish for a more realistic phonon density of states.