We investigate how additional topologically trivial metallic bands crossing the Fermi level modify the conventional quantum anomalous Hall (QAH)–superconductor mechanism for chiral topological superconductivity in ferromagnetic metals. A four-band model containing an inverted spin-polarized QAH sector and an exchange-split metallic pair is supplemented by spin-singlet $s$-wave pairing and studied in the Bogoliubov–de Gennes (BdG) formalism. Weak pairing produces a gapless or nearly gapless superconducting metal in which chiral boundary channels coexist with bulk quasiparticles and retain a dephasing-enhanced Hall response inherited from the metallic QAH parent state. Strong pairing gaps out the low-energy states derived from the normal-state metallic bands and stabilizes fully gapped two-dimensional chiral topological superconducting phases with BdG Chern numbers $\mathcal{N}=-2$ and $\mathcal{N}=1$. The evolution between the broad $\mathcal{N}=-2$ and $\mathcal{N}=1$ strong-pairing regimes proceeds through a narrow $\mathcal{N}=-1$ intermediate phase and is accompanied by a reversal of the net Majorana chirality and a pronounced reconstruction of the orbital texture of the chiral edge states. The fully gapped phases are identified by chiral Majorana ribbon spectra, quantized thermal Hall response, and Andreev transport signatures. Our results extend the QAH-superconductor paradigm to metallic ferromagnets and suggest ferromagnetic superconductors with spin-polarized band inversion as candidate platforms for intrinsic chiral topological superconductivity.

We investigate the temperature-dependent dynamical properties of ${\mathrm{PbZrO}}_3$ (PZO) using molecular dynamics (MD) simulations with an effective Hamiltonian. As temperature decreases from 1800  to 10 K, PZO is predicted to undergo a sequence of phase transitions. Above 1350 K, it exhibits the cubic paraelectric $Pm\overline{3}m$ phase. Between 1350  and 650 K, an intermediate phase emerges, denoted here as the $\mathrm{\Sigma }$ phase and characterized by antipolar displacements along [110] and complex oxygen octahedral tiltings about [001], both associated with the $\mathrm{\Sigma }$ point and with amplitudes increasing upon cooling. Below 650 K, PZO stabilizes in the $Pbam$ ground state, exhibiting additional $R$- and $S_4$-point order parameters, with all associated condensed degrees of freedom strengthening at lower temperatures. MD results yield a first-order character of the $Pm\overline{3}m$-to-$\mathrm{\Sigma }$ and $\mathrm{\Sigma }$-to-$Pbam$ transitions. Moreover, phonon analysis reveals the predicted temperature evolution of mode frequencies associated with $\mathrm{\Gamma }, R, \mathrm{\Sigma }$, and $S_{4}k$ points. In the cubic phase, $\mathrm{\Sigma }$, mode having both antipolar and octahedral tiltings characteristics is softening on temperature decrease, as consistent with the existence of a bilinear coupling that is often overlooked. In the $\mathrm{\Sigma }$ phase, a mode associated with the $R$-point-induced antiphase octahedral tiltings strongly softens. Within the $Pbam$ phase, multiple resonant frequencies appear for each mode, reflecting complex mode couplings, including bilinear and trilinear ones. These computations agree well with experimental data, including temperature behavior of soft mode and even a higher mode, which calls for testing all present predictions, that may offer new insight into key features of PZOs including its lattice dynamics and phase transitions.

The easy $c$-axis collinear antiferromagnetic order of the bilayer square-lattice iridate ${\mathrm{Sr}}_3{\mathrm{Ir}}_2{\mathrm{O}}_7$ has motivated a diverse range of microscopic models. A previous high-pressure Raman study suggested a magnetic phase transition near 15 GPa at low temperatures, but the fundamental nature of this transition has remained unclear. Here, we utilize high-pressure resonant inelastic x-ray scattering, x-ray absorption spectroscopy (XAS), and x-ray magnetic circular dichroism (XMCD) to directly probe the evolution of magnetic excitations in ${\mathrm{Sr}}_3{\mathrm{Ir}}_2{\mathrm{O}}_7$ under compression. We identify three distinct pressure regimes. At low pressures, the system hosts a well-defined magnon characteristic of long-range antiferromagnetic order. Beyond a characteristic pressure, the magnon broadens substantially while its energy continues to harden, marking a crossover into a heavily damped paramagnon regime. Upon further compression, the paramagnon spectral weight is fully suppressed at a distinct second boundary. Both the crossover and the phase boundary exhibit a pronounced temperature dependence, shifting to higher pressures at lower temperatures. The crossover pressure lies near the previously identified Raman transition, whereas the second boundary extends beyond 22.5 GPa at 33 K. Throughout the explored pressure-temperature phase space, XAS and XMCD spectra reveal no discernible changes, ruling out any substantial departure from the $J_{\mathrm{eff}}=1/2$ state or a transition to an alternative magnetic configuration such as a spin-flip phase. We discuss these findings in the context of the competing microscopic models for magnetism in ${\mathrm{Sr}}_3{\mathrm{Ir}}_2{\mathrm{O}}_7$.

Magnetoresistance of hole-doped ${\mathrm{LaMnO}}_3$ at frequencies above a few MHz has been seldom reported compared to numerous studies on magnetoresistance measured at direct current. Here, we contrast the high-frequency magnetoresistance in the frequency range $f=0.9–3\mathrm{GHz}$ in polycrystalline ${\mathrm{LaMnO}}_3$ (LMO) synthesized by microwave irradiation of oxide precursors in a microwave furnace (MW-LMO) and by conventional heating (CH-LMO) in an electrical furnace. The structure at room temperature changes from orthorhombic in CH-LMO to rhombohedral in MW-LMO. A combination of magnetization and resistivity studies suggests that the CH-LMO sample is a canted antiferromagnetic insulator below 140 K but the MW-LMO is a ferromagnetic metal with $T_C=240\mathrm{K}$. While the high-frequency resistance of the CH-LMO sample at 300 K decreases gradually with increasing strength of the applied dc magnetic field for all $f$, a peak appears at $H=H_r>0$ when $f\ge 1.4\mathrm{GHz}$ in the MW-LMO sample and $H_r$ increases linearly with $f$. We attribute the observed features in the high-frequency magnetoresistance of MW-LMO to current-driven resonant excitation of spins in the paramagnetic state. Its absence in the CH-LMO sample highlights the need for an optimum hole density to observe this effect.

Using the magnetostatic approximation, we calculate the spectra of bulk and surface spin waves in an in-plane magnetized ferromagnet/paramagnet bilayer. Due to the dipolar coupling between the layers, the paramagnet becomes polarized, which in turn modifies the spectrum of the Damon-Eshbach magnetostatic modes. We assume that the paramagnet is characterized by a magnetic susceptibility, $\chi \propto 1/(T-T_C)$, which reaches large values when the system temperature $T$ is close to the Curie temperature $T_C$. We find the conditions under which surface spin waves become unidirectional, i.e., capable of carrying energy in only one direction, and determine the magnitude of their frequency nonreciprocity. We demonstrate the possibility of switching the unidirectional wave regime on and off by varying the external magnetic field or temperature, making the ferromagnet/paramagnet system an attractive platform for tunable magnonic logic devices.

The real mechanism of ferromagnetism in III-V diluted magnetic semiconductors such as ${\mathrm{Ga}}_{1-x}{\mathrm{Mn}}_x\mathrm{As}$ is still debated. The experimental results point out the realization of appreciable ferromagnetism at filling of the impurity band close to one-half that can be expressed in terms of compensation degree. Based on our recent results on the existence of two competing mechanisms of pair indirect exchange (with ferro- and antiferro alignment of Mn $d$ shells), a theory of magnetic ordering in (Ga,Mn)As is presented. The molecular-field-like equation is derived in which the effective exchange constant contains all necessary information about material, including the Mn content, the compensation degree, the crystal coordination, and the parameters of two competing pair exchange interactions. The Curie temperature depends crucially on the compensation degree. Depending on Mn content and compensation degree, three possible magnetic phases (paramagnetic, ferromagnetic, and spin-glass-like) are predicted. However, the spin-glass-like phase in (Ga,Mn)As is apparently not realized due to the additional inevitable compensation caused by As antisites. The phase transition into the ferromagnetic state occurs not only with Mn content variation but through the change of the compensation degree as well. The new mechanism of photoferromagnetic effect is predicted and discussed in the context of possible clarification of the magnetic ordering mechanism. It is assumed that the main obstacle to a possible increase in the Curie temperature is the increasing contribution of the antiferromagnetic superexchange between the nearest-neighbor Mn's, rather than compensatory (electric or magnetic) effects from Mn interstitials, as was previously stated. The comparison of our predictions with available experimental data is presented.

We report a ${}^{23}\mathrm{Na}$-NMR study of the alkali superoxide ${\mathrm{NaO}}_2$, a candidate one-dimensional quantum spin system. The Knight shift, linewidth, and spin-lattice relaxation rate $1/T_1$ were investigated down to 0.3 K in magnetic fields up to 16 T. Below $T_{\mathrm{S}3}=34\text{K}$, $1/T_1$ exhibits thermally activated behavior, indicating the opening of a spin gap of $\mathrm{\Delta }\left(10.1\mathrm{T}\right)\simeq 38.0\text{K}$ and $\mathrm{\Delta }\left(3.55\mathrm{T}\right)\simeq 46\text{K}$. The hyperfine coupling constant shows a sudden reduction across the structural transition at $T_{\mathrm{S}2}\simeq 195\text{K}$, reflecting the development of pronounced one-dimensionality in the electron structure. These results provide microscopic evidence that ${\mathrm{NaO}}_2$ is a rare $\pi$-orbital-based one-dimensional spin chain that exhibits a spin-gapped ground state, consistent with a spin-Peierls-like instability.

Recent studies on ferrimagnetic systems have revealed conflicting trends in spin-orbit-torque-related responses near magnetic compensation, as exchange coupling and net magnetization are typically varied simultaneously. Here, we employ a perpendicularly magnetized Pt/Co/IrMn trilayer with interfacial exchange coupling as a model system, where the exchange-bias magnitude and remanent magnetization configuration can be separately varied within a single device by controlling the IrMn antiferromagnetic state. We find that the measured damping-like effective field at low temperature is gradually suppressed with increasing exchange-bias magnitude. In contrast, room-temperature measurements of reduced-remanence states follow the expected $1/\left|x\right|$ averaged-response scaling. This suggests that, in the present exchange-biased Pt/Co/IrMn trilayer, the magnetization configuration alone does not produce an anomalous damping-like effective field response in Co.

The single-layer cuprate superconductor ${\mathrm{HgBa}}_2{\mathrm{CuO}}_{4+\delta }$ (Hg1201) is an ideal candidate for investigating many properties of cuprates with minimal disorder and without the complication of multiple ${\mathrm{CuO}}_2$ layers. Here we measure the in-plane longitudinal thermal conductivity $\kappa$ of underdoped Hg1201 ($T_c$ = 76 K, $p$ = 0.11) at dilution refrigerator temperatures to extract the nodal quasiparticle velocity ratio $v_F/v_{\mathrm{\Delta }}$. Assuming contributions from only a single line node per quadrant on the Fermi surface leads to a value of $v_F/v_{\mathrm{\Delta }}$ = $23\pm 3$, anomalously large compared to other cuprates at similar dopings. In conjunction with the anomalously high quasiparticle specific heat of Hg1201 in the normal state reported previously at a similar doping, this points to more than one Fermi surface sheet crossing the nodal line, suggesting the presence of more than the single small electron pocket detected by quantum oscillations.

We formulate the tight-binding model for cubic $\alpha$-Sn based on the density functional theory calculations. In the model, we incorporate a variable bond angle, which allows us to simulate the effect of the in-plane strain. In the bulk, we demonstrate the presence of the ${\mathbb{Z}}_2$ topological invariant and a nonzero mirror Chern number, making $\alpha$-Sn one of the rare cases where dual topology can be observed. We calculate the topological phase diagram of multilayer $\alpha$-Sn as a function of strain and number of layers. We find that a nontrivial quantum spin Hall state appears only for compressive strain above five layers of thickness. Quite surprisingly, both in the trivial and nontrivial phases, we find a plethora of edge states with energies inside the bulk gap of the system. Some of these states are localized at the side surfaces of the slab and some of them prefer top and bottom surfaces. We find that they can be adiabatically connected to topological states in the chiral limit, where the model supports multiple one-dimensional winding numbers that take different values in different directions in the Brillouin zone. Finally, around high-symmetry points their presence can also be explained by the mirror Chern number and Wilson-loop invariants.

The fundamental behavior of hydrogen in relation to the magnetism of nanoscale quantum magnets holds considerable significance within the fields of Kondo physics and spintronics. However, the precise atomic-scale manipulation of molecular spin states and their associated Kondo effects remains a significant challenge. In this study, we theoretically establish that selective hydrogen adsorption can significantly modulate the magnetic characteristics of a single cobalt phthalocyanine (CoPc) molecule adsorbed on an Au(111) substrate. This modulation facilitates the manipulation of the molecular Kondo state, thereby enabling the operation of a Kondo switch. First-principles calculations reveal that the combined influence of reduced structural distortion and elongation of the Co–Au distance upon sufficient hydrogenation leads to a weakened interaction between the adsorbed molecule and the substrate, accompanied by charge redistribution within the molecule. These modifications substantially alter the system's magnetic moment, increasing it from $0{\mu }_{\mathrm{B}}$ to $1.67{\mu }_{\mathrm{B}}$ in the ${\mathrm{H}}_4\text{−}\mathrm{CoPc}/\mathrm{Au}\left(111\right)$ complex. Electronic structure analysis indicates that the spin density localized at the Co center arises from magnetism associated with localized $d$-electrons, whereas the spin density distributed over the Pc ring corresponds to magnetism derived from delocalized $\pi$-electrons. Furthermore, the adsorption of a fifth hydrogen atom atop the central Co ion quenches the molecular magnetism to a nonmagnetic state. The spin-state-switching mechanism observed in the CoPc/Au(111) system serves as a representative model for a potential Kondo switch and provides significant insights for the experimental control and design of collective quantum magnetism in analogous systems.

Depth-dependent electronic states of a prototypical strongly correlated ${\mathrm{Fe}}_3{\mathrm{O}}_4$ thin film across the Verwey transition temperature $(T_{\mathrm{V}}\sim 125\mathrm{K})$ were investigated by hard x-ray photoemission spectroscopy (HAXPES) combined with x-ray total reflection (TR). We found that the Fe $2p$ HAXPES spectral shapes strongly depend on the effective inelastic mean-free-path (${\lambda }_{\mathrm{eff}}$) regardless of temperature ($T$). Particularly, the shoulder structure located at the lower binding energy side of the Fe $2p_{3/2}$ main peak becomes more pronounced with increasing ${\lambda }_{\mathrm{eff}}$ (i.e., increasing bulk sensitivity), indicating a significant difference in the electronic structures between the surface and deeper regions of the film. This trend coincides with the increase of the density of states near the Fermi level $\left(E_{\mathrm{F}}\right)$ for larger ${\lambda }_{\mathrm{eff}}$, suggesting the contribution of nonlocal screening effects. While the valence band spectra show a clear metal-to-insulator transition across $T_{\mathrm{V}}$, the Fe $2p$ core-level HAXPES and the magnetic circular dichroism profiles for large ${\lambda }_{\mathrm{eff}}$ are almost independent on $T$. This behavior suggests that the average valence of the $B$-site Fe species is maintained at 2.5+ across $T_{\mathrm{V}}$. Comparison with the configuration interaction theory based on the cluster model calculations emphasizes the importance of nonlocal screening effects in the Fe $2p$ spectral shapes. Our results demonstrate that HAXPES combined with TR is a powerful technique for probing systematic depth-dependent electronic states. By providing this systematic dataset from the surface to deeper regions, this work serves as a reliable benchmark for the research field.

We propose an altermagnetism-induced route to a two-dimensional higher-order topological Dirac semimetal in a trilayer nonsymmorphic Dirac system. Interlayer hybridization preserves the nonsymmorphic bulk Dirac crossings and generates helical edge states in the trilayer phase. Introducing outer-layer $d$-wave altermagnetic order gaps the helical edge states, while only the symmetry-protected Dirac crossing at the high-symmetry point $M$ remains gapless. The resulting phase hosts a surviving bulk Dirac point, gapped edge spectra, and corner states. An exact layer-space decomposition further reveals that these features arise from the coexistence of a gapless Dirac sector and a gapped ${\mathbb{Z}}_2$ topological sector. Our results establish altermagnetism as an effective mechanism for engineering higher-order topological Dirac semimetals in two-dimensional nonsymmorphic systems.

Developing a general and rigorous analytical approach to non-Hermitian many-body systems is a challenging task. Here, we generalize the eta-pairing theory to very general non-Hermitian Hubbard models and find many interesting phenomena without Hermitian analogs. For instance, the Hermitian conjugate of an eta-pairing eigenoperator may not be an eigenoperator, eta-pairing eigenoperators can be spatially modulated, and the $SU\left(2\right)$ pseudospin symmetry may not be possible even if the $\mathrm{Hamiltonian}$ commutes with the eta-pairing operators. Remarkably, these interesting non-Hermitian phenomena are closely related to each other by several theorems we establish and can lead to, for example, new types of eta-pairing operators (e.g., the notion of non-Hermitian angular-momentum operators) and Fock-space localization of many-body eta-pairing eigenstates. Some issues on the $SO\left(4\right)$ and particle–hole symmetries are clarified. Our general eta-pairing theory also reveals a previously unnoticed unification of these symmetries of the Hubbard model. These general results can be illustrated with concrete examples such as the generalized Hatano–Nelson–Hubbard models and a general two-sublattice model. In particular, the general two-sublattice model can reveal the eta-pairing structure [e.g., the $SO\left(4\right)$ symmetry] in systems with Hermitian hoppings, including the original eta-pairing theory for the square lattice, the extension to the triangular lattice, and some topological systems. Our results establish a rigorous theoretical framework for studying interacting non-Hermitian systems in arbitrary spatial dimensions, even without bulk translation symmetry.

We present a microscopic quantum transport mechanism for microwave-induced resistance oscillations (MIROs) based on microwave-driven coherent states. By evaluating the impurity scattering matrix element between driven states, we show that the instantaneous scattering rate becomes dynamically synchronized with the velocity of the radiation-induced motion. The resulting velocity-dependent scattering provides a direct microscopic origin for the finite time-averaged transport response underlying MIROs. We further introduce a geometric dephasing mechanism arising from the accumulated displacement of the driven coherent state, which limits the oscillation amplitude at high microwave power. This mechanism naturally explains the observed crossover from linear to sublinear power dependence and predicts a magnetic-field-dependent saturation scale governed by the ratio between the driven displacement amplitude and the cyclotron radius. Our results establish a coherent-state picture of MIROs in which transport is controlled by synchronized scattering and geometric decoherence.

The magnon thermal Hall and spin Hall effects (SHE) driven by surface acoustic wave (SAW)-induced pseudogauge fields have been investigated in two-dimensional honeycomb compensated ferrimagnets (CFMs). Unlike antiferromagnets, where the magnon thermal Hall effect is prohibited by the degeneracy of the two magnon branches, CFMs exhibit a finite thermal Hall response because unequal easy-axis anisotropies on the two magnetic sublattices lift this degeneracy. The resulting energy splitting between the magnon branches creates a population imbalance, leading to a thermal Hall conductivity that is readily tuned by the anisotropy difference. In contrast, the SHE remains finite even in the absence of magnon-band splitting and shows only a weak dependence on the anisotropy difference. The role of four-magnon interactions is then examined within the Hartree-Fock approximation. It is found that magnon-magnon interactions suppress both the thermal Hall and spin Hall responses compared with the predictions of noninteracting linear spin-wave theory. These findings identify CFMs as a promising platform for strain-controlled magnon-mediated thermal and spin transport.

We consider the problem of Coulomb drag in interactively coupled quantum circuits built of adiabatic constrictions: quantum point contacts and short quantum-wire channels. The interplay of spatial confinement and magnetic field leads to a rich oscillatory response of the drag current as a function of gate voltage and magnetic field: drag peaks track the depopulation of magnetoelectric subbands, are asymptotically periodic in inverse field, and their visibility is controlled by the competition of temperature with the field-sharpened tunneling width of the constriction. We derive a closed expression for the linear drag conductance whose interaction kernel simplifies dramatically in the experimentally relevant limit of a long thermal length compared with the range of the interwire coupling, investigate the drag in the nonlinear regime, where the drag current measures the transconductance of the drive channel at any field, and discuss physically motivated models of dissipation-induced nonreciprocity of the drag signal. Extensions accounting for Zeeman splitting, interaction renormalization of the barrier transmission, backscattering at high field, and the frequency structure of the circuit coupling delineate how each mechanism imprints itself on the temperature dependence and line shapes of the drag oscillations.

Singlet-only always-on gapless exchange (SAGE) spin qubits are an alternative type of exchange-only (EO) qubits that encode a single qubit in the spins of four electrons located in four tunnel-coupled quantum dots. While conventional EO qubits are susceptible to local magnetic field gradients caused by local nuclear environments and $g$-factor variations, the SAGE qubit subspace is inherently protected from magnetic-gradient-induced Pauli errors by virtue of the singlet-only encoding, which is invariant under magnetic field gradients, and the always-on exchange couplings, which provide energetic leakage protection. However, the always-on operation simultaneously increases the qubit's sensitivity to charge noise. Here, starting from a Hubbard model describing the underlying electronic structure of the coupled quantum dots, we characterize the performance of SAGE qubits in the presence of $1/f$ charge noise that induces fluctuations in both the dot chemical potentials and the interdot tunnel couplings. We calculate SAGE idle coherence times and show that realistic Carr-Purcell-Meiboom-Gill–like pulse sequences can be used to significantly extend SAGE single-qubit coherence times for experimentally relevant charge noise strengths. We likewise study the fidelity of SAGE two-qubit gates in the presence of charge and magnetic noise and again propose a simple refocusing strategy to mitigate the noise, while increased ramp times of the entangling pulse suppress leakage into noncomputational states.

We investigate the non-Hermitian skin effect (NHSE) and topological phases in a ladder model with staggered nonreciprocal interleg hopping, consisting of a Su-Schrieffer-Heeger chain coupled to a normal tight-binding chain. By tuning the system parameters, we show that the direction of the NHSE under open boundary conditions can be reversed and can even become energy dependent. The NHSE is further characterized by the spectral winding number under periodic boundary conditions. We also demonstrate that the interleg coupling significantly enlarges the topologically nontrivial parameter regime. Remarkably, there are two topological phases characterized by winding numbers $W=\pm 1$, with the zero-energy topological edge modes residing on different sites in the two legs. Furthermore, increasing the nonreciprocity of the interleg hopping modifies the topological phase boundaries and eventually drives the system into a topologically trivial phase. Our results establish staggered nonreciprocal interleg hopping as an effective mechanism for engineering both the non-Hermitian skin effect and topological phases in ladder systems.

We show that the broad x-ray photoelectron lines of silicon oxide on silicon arise from a continuous statistical distribution of core-level binding energies. Statistical simulations spanning compositions from Si to ${\mathrm{SiO}}_2$ reproduce the full extent of this broadening, reaching $\sim 5\mathrm{eV}$ for ${\mathrm{SiO}}_{1.0}$, in quantitative agreement with 0.23-nm layer-resolved spectra reconstructed from ${\mathrm{Ar}}^{+}$ sputtering data. This continuous distribution blurs distinct spectral fingerprints of local structural motifs, thereby challenging conventional chemical state assignment in oxide x-ray photoelectron spectra.