Antiferromagnetic materials feature zero net magnetization, robustness against external magnetic fields, negligible stray fields, and ultrafast terahertz spin dynamics, making them promising candidates for spin-based applications. However, the measurement of the Néel order for antiferromagnets with $\mathcal{PT}$ symmetry remains a challenge for existing experimental techniques. In this Letter, we propose an electrical method to detect the Néel order in $\mathcal{PT}$-symmetry-protected $\gamma$-FeMn by constructing a ${\mathrm{Cu}}_3\mathrm{Al}|\gamma$-FeMn interface. In which, we observe that the anomalous Hall current and spin-transfer torque are all strongly coupled to the Néel order. Moreover, we extend the tensor theory to describe the relationship between the Néel order and the transport properties under interface-induced symmetry breaking. This theory agrees well with our calculated results, demonstrating that interface symmetry breaking is essential for detecting the Néel order. Our results show that the detection and manipulation of antiferromagnets can be achieved using only electrical methods, facilitating the development of nonvolatile spin memory and logic devices.

We propose two distinct crosscap states for the two-dimensional (2D) Ising field theory. These two crosscap states, identifying Ising spins or dual spins (domain walls) at antipodal points, are shown to be related via the Kramers-Wannier duality transformation. We derive their Majorana free field representations and extend bosonization techniques to calculate correlation functions of the 2D Ising conformal field theory (CFT) with different crosscap boundaries. Away from criticality, we develop a conformal perturbation theory to calculate the Klein bottle entropy (norm-square of the crosscap overlap) as a universal scaling function [Phys. Rev. Lett. 130, 151602 (2023)]. For the Ising field theory, our analytical results support the conjectured monotonicity of the Klein bottle entropy under relevant perturbations. The formalism provides a general framework for studying perturbed 2D CFTs on nonorientable manifolds.

The chemistry and atomistic structure of amorphous silica-based compounds under high-pressure conditions are intricately connected to numerous macroscopic properties of the Earth's mantle. To improve the understanding of their properties, detailed insights into pressure-induced structural changes in amorphous silicates is required. Among silicates, highly studied amorphous silica and alkali-earth silicates such as ${\mathrm{MgSiO}}_3$ glass have been considered as reference compounds during high-pressure studies. However, magnesium atoms have a significantly larger ionic radius compared to silicon and oxygen. Alkali-earth silicates may therefore not be suitable to study the densification behavior of amorphous silicates containing low-Z cations under pressure. In this study, we follow the pressure-induced structural changes in the partially depolymerized lithium metasilicate glass ${\mathrm{Li}}_2{\mathrm{SiO}}_3$ using x-ray Raman scattering spectroscopy at the Si ${\mathrm{L}}_{2,3}$ and O K edges as well as ab initio molecular dynamics simulations and subsequent spectrum simulations based on the Bethe-Salpeter equation. At low pressure, topological rearrangements of the Si-O network lead to an increase of its degree of polymerization. Higher-coordinated silicon and oxygen atoms gradually form at pressures above 15 GPa in contrast to the abrupt amorphous-amorphous transition in the pure parent compound ${\mathrm{SiO}}_2$. This gradual transition from ${}^{\left[4\right]}\mathrm{Si}$ to ${}^{\left[6\right]}\mathrm{Si}$ and ${}^{\left[2\right]}\mathrm{O}$ to ${}^{\left[3\right]}\mathrm{O}$ is expected to affect various macroscopic properties of alkali silicates glasses, especially those involving ion transport.

We report the anisotropic magnetic properties of single-crystal CrSBr. Isothermal magnetization studies are performed to elucidate the magnetic and magnetocaloric properties. An important finding is a rapid shift in the peak of the magnetic entropy change; from approximately 132 K at 0.1 T to 170 K at 9 T across both in-plane crystallographic directions, $a$ and $b$ axes and132 K at 0.1 T to 159 K at 9 T along the out-of-plane hard $c$ axis. This rapid shifting with the increasing magnetic field signifies the intralayer ferromagnetic correlation above Neel temperature $(T_{\mathrm{N}}=132\mathrm{K})$. Moreover, the antiferromagnetic phase in the low magnetic field regime exhibits a first-order magnetic phase transition, and the field-induced ferromagnetic phase has a second-order magnetic phase transition. Additionally, the analysis of the relative cooling power (RCP) and full width at half maximum (FWHM) of the magnetic entropy change, along with the obtained critical exponents for the three orientations, suggests that the magnetic phase transition in CrSBr exhibits three-dimensional critical behavior. Magnetic-field-dependent polarized Raman spectroscopy confirms the strong spin-phonon coupling in this material.

Protecting superconducting qubits from low-frequency noise by operating them on dynamical sweet-spot manifolds has proven to be a promising setup, theoretically as well as experimentally. These dynamical sweet spots are induced by an externally applied Floquet drive, and various drive forms have been studied in different types of qubits. In this work we study the effects of using two-tone drives on the applied magnetic flux of the form ${\varphi }_{\mathrm{ac}}\left(t\right)={\varphi }_{m}cos\left(m{\omega }_{\mathrm{d}}t\right)+{\varphi }_{n}cos(n{\omega }_{\mathrm{d}}t+\phi )$, where $m,n\in {\mathbb{N}}_{>0}$, on the coherence times of fluxonium qubits. Through analysis using perturbation theory in the strong-drive limit, we show which sets of drive parameters increase the dephasing times, based upon first-order coupling between Floquet modes. These are further analyzed using numerical calculations. We further show that this type of drive allows for more tunability of the quasienergy spectrum, creating higher and wider peaks of the dephasing time without affecting the relaxation times too strongly. Lastly, we show that temporarily modulating the drive form using a second commensurable tone can be used to implement an improved phase gate compared to implementations with a single tone, supported by Monte Carlo simulations.

Combining superconductivity with spintronics provides exciting opportunities to realize low-dissipation quantum devices. Here we report the synthesis, characterization, and magnetotransport measurements of the $\mathrm{Pb}\text{/}{\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_{8+\delta }$ (BSCCO) superconducting heterostructures, where an insulating ${\mathrm{PbO}}_x$ layer spontaneously forms at the interface. Nonvolatile switching between superconducting (logical “0”) and normal (“1”) states in Pb films by an external field, i.e., infinite magnetoresistance (IMR), can be realized and are attributed to the strong trapping and pinning of vortices in BSCCO. Furthermore, butterfly-shaped hysteresis loops in magnetoresistance, pronounced resistance dips and jumps, and thermal reset to superconducting states can be observed and are direct manifestations of the peculiar vortex dynamics in BSCCO and vortex coupling across the Pb/BSCCO interface. Our work demonstrates a simple and effective way to realize IMR through superconducting vortices and opens up opportunities to study the vortex interactions across the superconducting interfaces.

Signatures of unconventional superconductivity have been recently observed in certain transition metal dichalcogenides (TMDs), including $4{\mathrm{H}}_b\text{−}{\mathrm{TaS}}_2$ and monolayer 2H-${\mathrm{NbSe}}_2$. While the pairing channel remains unknown, it has been argued that spin fluctuations can stabilize pairing in the two-component $E^{\prime }$ channel, a $p$-wave spin-triplet state which could be consistent with some of the reported signatures. Exploiting the particular multiorbital character of the Fermi surface and the presence of Ising spin-orbit coupling, which enable finite optical conductivity in the clean limit, in this work we predict clear-cut optical signatures to detect and distinguish the chiral and nematic ground states of the $E^{\prime }$ pairing. We quantify how nematic $E^{\prime }$ states produce a diagonal anisotropy ${\sigma }_{xx}\ne {\sigma }_{yy}$ due to the broken threefold symmetry ($C_3$), while chiral $E^{\prime }$ states yield a finite optical Hall conductivity ${\sigma }_{xy}^H$ due to broken time-reversal symmetry, and find both signals could be detected in current experiments. For instance, for realistic gaps in the meV range, we predict a relative anisotropy $\mathrm{\Delta }\sigma /\sigma \sim {10}^{-5}$ in the nematic states, and a polar Kerr rotation of ${\theta }_K\sim {10}^{-5}\mathrm{rad}$ in the chiral states. These symmetry fingerprints provide a practical route to distinguish nematic and chiral superconducting order in TMD superconductors.

We develop the Ginzburg-Landau-Devonshire phenomenological model for trigonal ferroelectrics, which matches experimental values of the poling electric field for both near-stoichiometric and congruent compounds. The model favors a non-Ising type of polarization switching. Therefore, domain walls have nontrivial Néel and/or Bloch polarization components supported by numerical computations. Néel and/or Bloch polarization components are of the order from 1 to 10% of spontaneous polarization in the model. Numerically calculated optimal domain wall profile has bichiral Bloch behavior for near-stoichiometric ${\mathrm{LiTaO}}_3$ and ${\mathrm{LiNbO}}_3$ and congruent lithium niobate. The domain wall has a mixed Bloch-Néel type without including electrostatic interactions and has a Bloch character when nonlocal electrostatic interactions are accounted for in congruent lithium tantalate.

We report the $c$-axis resistivity measurements of ${\mathrm{FeTe}}_{0.6}{\mathrm{Se}}_{0.4}$ single-crystalline lamellae, extracted by using focused ion beam techniques, and determine the upper critical fields $H_{\mathrm{c}2}$ for $H\parallel c$ and $H\parallel ab$ down to 1.3 K. In contrast to early results based on the in-plane resistivity measurements, $H_{\mathrm{c}2}$ for $H\parallel c$ ($H_{\mathrm{c}2}^c$) shows a rapid increase just below the superconducting transition, at almost the same rate with that of $H_{\mathrm{c}2}$ for $H\parallel ab$ ($H_{\mathrm{c}2}^{ab}$). The whole temperature dependence of $H_{\mathrm{c}2}^c$ and $H_{\mathrm{c}2}^{ab}$ indicates that the Pauli pair-breaking effects become dominant for both $H_{\mathrm{c}2}^c$ and $H_{\mathrm{c}2}^{ab}$ of ${\mathrm{FeTe}}_{0.6}{\mathrm{Se}}_{0.4}$ where excess Fe is sufficiently removed. The quantitative comparison between the $c$-axis charge transport study in this work and the previous studies reveals that the magnetic pair-breaking mechanism is essentially independent of the current direction in the charge transport and that the details of $H_{\mathrm{c}2}\left(T\right)$ strongly depend on the excess Fe content.

The coupling between quasiparticles and bosonic excitations rules the energy transfer pathways in condensed matter systems. The possibility of inferring the strength of specific coupling channels from their characteristic timescales measured in nonequilibrium experiments is still an open question. Here, we investigate ${\mathrm{MgB}}_2$, in which conventional superconductivity at temperatures as high as 39 K is mediated by the strong coupling between the conduction electrons and the $E_{2g}$ phonon mode. By means of broadband time-resolved optical spectroscopy, we show that this selective electron-phonon coupling dictates the nonequilibrium optical response of ${\mathrm{MgB}}_2$ at early times ($<100\mathrm{fs}$) after photoexcitation. Furthermore, based on an effective temperature model analysis, we estimate its contribution to the total electron-boson coupling function extracted from complementary equilibrium spectroscopy approaches, namely, optical reflectivity and angle-resolved photoemission spectroscopy. The coupling strength with the $E_{2g}$ phonon modes is thus estimated to be $\lambda \simeq$ 0.56, which is approximately half of the total coupling constant, in agreement with $\mathit{ab}$ initio calculations from the literature. As a benchmark, broadband time-resolved optical spectroscopy is performed also on the isostructural and nonsuperconducting compound ${\mathrm{AlB}}_2$, showing that the nonequilibrium optical response relaxes on a slower timescale due to the lack of strongly coupled phonon modes. Our findings demonstrate the possibility to resolve and quantify selective electron-phonon coupling from nonequilibrium optical spectroscopy.

Quantum dot platforms have enabled the direct observation of Nagaoka ferromagnetism (NFM) in small arrays and noninfinite interaction strength. However, optimizing the cluster connectivity characteristics that yield a ground state with maximal spin and their robustness against magnetic fields remains unexplored. Employing exact diagonalization of the Hubbard Hamiltonian, we find a connection between the existence of kinetic ferromagnetism and graph theory descriptions. Algebraic connectivity (${\lambda }_2$) and Katz centrality (KC) are shown to be related to the spin correlation over the system. In square arrays, the onset of NFM is found to be $t_c/U\simeq {\lambda }_2^2$. In optimal cluster geometries, large ${\lambda }_2$ and low KC fluctuation per site are found to enhance $t_c/U$, extending the NFM phase while diminishing the strength of spin-correlation clouds. A perpendicular magnetic field introduces Aharonov-Bohm phases, and a critical flux for which NFM is destroyed. We further find that tuning the flux phase to $\pi$ results in a ground state that exhibits antiferromagnetic correlations (counter-Nagaoka state). Our results illustrate how NFM and polaron formation can be predicted from the array's connectivity (${\lambda }_2$ and KC), and how the introduction of flux results in the counterintuitive destruction of kinetic ferromagnetism in the system.

We report Ru $L_3$-edge resonant X-ray diffraction studies on single-crystal and (001)-oriented epitaxial films of ${\mathrm{RuO}}_2$. We investigate the distinct $\mathbf{Q}=\left(100\right)$ and (001) Bragg-forbidden reflections as a function of incident energy, azimuthal angle, and temperature. The results show that the observed resonant diffraction in ${\mathrm{RuO}}_2$ is fully consistent with a resonant charge anisotropy signal of structural origin permitted by the parent (nonmagnetic) rutile $P{4}_2/mnm$ space group. These results significantly constrain the magnetic contribution to the resonant diffraction signal and indicate the unlikely existence of $\mathbf{k}=\mathit{0}$ antiferromagnetic order in ${\mathrm{RuO}}_2$.

We present a non-Hermitian model with gain/loss and nonreciprocal next-nearest-neighbor hopping that emulates black-hole physics. The model describes a one-dimensional lattice with a smooth connection between regions with distinct hopping parameters. By mapping the system to an effective Schwarzschild metric in the Painlevé-Gullstrand coordinates, we find that the interface is an analogue to a black-hole event horizon. We obtain emission rates for particles and antiparticles, the Hawking temperature, the Bekenstein-Hawking entropy, and the mass of the analogue black hole as a function of the interface sharpness and the system parameters. An experimental realization of the theoretical model is proposed, thus opening the way to the detection of elusive black-hole features.

We report on an investigation of the low-temperature structural, thermal, and magnetic properties of the binary trifluoride ${\mathrm{VF}}_3$ by temperature-dependent magnetization, heat capacity, electron paramagnetic resonance, and synchrotron powder and neutron powder diffraction measurements. At room temperature the crystal structure of ${\mathrm{VF}}_3$ features ${\mathrm{V}}^{3+}$ spin $S$ = 1 regular triangular layers. At $\sim 120\mathrm{K} {\mathrm{VF}}_3$ undergoes a structural phase transition, and at $\sim 18\mathrm{K}$ it undergoes an antiferromagnetic phase transition. The structural phase transition involves a minute orthorhombic distortion of the regular octahedral fluorine coordination shell of the trivalent V cations, effecting a distortion to the monoclinic crystal system. The magnetic phase transition generates a weak ferromagnet with V magnetic moments essentially confined to the trigonal planes of the room temperature structure described in the space group $R-3c$. The ordered magnetic moments of the ${\mathrm{V}}^{3+}$ cations amount to $\approx 1{\mu }_{\mathrm{B}}$ and is thus distinctly reduced from the spin-only magnetic moment of $2{\mu }_{\mathrm{B}}$. This finding and the weak ferromagnetic moment are discussed in view of the low-symmetry structure and spin-orbit effects on the ${}^3{T}_1$ cubic ground term of the ${\mathrm{V}}^{3+} d^2$ system.

${\mathrm{Mn}}_2{\mathrm{Bi}}_2{\mathrm{Te}}_5$, a layered magnetic topological insulator, provides an ideal platform for studying the pressure-tuned interplay between magnetism and topology. Using first-principles density functional theory and Monte Carlo simulations, we examine its structural, magnetic, and electronic evolution under hydrostatic pressures up to 18 GPa. The lattice compresses anisotropically without crystallographic symmetry breaking, and the A-type antiferromagnetic ground state remains robust, with uniaxial anisotropy that favors the $z$ axis throughout. An approximate Mn–Mn crossover distance of 4.15 Å accounts for the sign change of the in-plane exchange coupling $J_2$ over 3 GPa to 6 GPa, thereby reconciling partial deviations of the computed exchange parameters with the Goodenough-Kanamori-Anderson rules. We find no evidence for exchange cancellation within a nonuple-layer unit; instead, the interplane exchange couplings $J_1$ and $J_3$ increase cooperatively under pressure. The Néel temperature nearly doubles, rising from 21 K to about 40 K at 18 GPa, consistent with a fourfold increase in magnetic anisotropy energy and strengthened interplane exchange couplings. Electronically, pressure removes the ambient band inversion by a few gigapascals and drives the bulk gap toward closure between 18 GPa and 19 GPa. Overall, these results demonstrate that hydrostatic pressure simultaneously enhances magnetic order and tunes band topology in ${\mathrm{Mn}}_2{\mathrm{Bi}}_2{\mathrm{Te}}_5$, establishing it as a model system for pressure-controlled magnetism-topology interplay in layered quantum materials.

We employed the self-consistent method on a two-orbital type-II time-reversal-symmetric Weyl semimetal, revealing a hybrid pairing of singlet $s$ wave and triplet $p$ wave. We present a detailed analysis of the normal-state electronic structure and the self-consistent results. Our findings indicate that the selection of hybrid pairings is governed by distinct surface Fermi-arc configurations: specifically, $s$-wave pairing dominates on the bottom surface, while $p$-wave pairing prevails on the top. Furthermore, the emergent superconducting state is a second-order topological superconductor with hinge states in the system. Our results identify type-II time-reversal-invariant Weyl semimetals as a promising intrinsic platform for realizing unconventional and topological superconductivity.

Despite of the low transition temperature, the recently identified superconductor ${\mathrm{CeRh}}_2{\mathrm{As}}_2$ has garnered significant interest due to its unique symmetry and magnetic characteristics, particularly the existence of two superconducting phases under a magnetic field, one of which exceeds the Pauli-Clogston limit. The field-induced transition from a low-field even-parity superconducting state to a high-field odd-parity state is usually described as a singlet-triplet transition. However, it is uncommon for a single compound to exhibit both triplet and singlet superconducting scenarios. The aim of this paper is to investigate the possibilities of symmetry changes in the superconducting state without a change of spin multiplicity. To this end, we construct the superconducting order parameter (SOP) of ${\mathrm{CeRh}}_2{\mathrm{As}}_2$ based on Anderson pair functions, considering the phase winding within the symmetry of the point group $D_{4h}$ and the magnetic group $4/m{m}^{\prime }{m}^{\prime }$. It was found that two triplets with opposite-spin and equal-spin pairing states of symmetry $E_{1u}^{\prime +}$, are nodeless but exhibit distinct internal structures and may be associated with low- and high-field phases. Additionally, nontrivial Cooper pairing resulting from the nonsymmorphic structure of the space group was examined, particularly in the case where the Fermi surface intersects with the boundaries of a BZ (Brillouin zone). It was determined that at the $\mathrm{X}$ point, triplet pairs are even, while singlet pairs can be either even or odd. Furthermore, at the $\mathrm{X}$ point, pair density waves that alter phase by $\pi$ at the atomic centers linked by lattice translations are also feasible. To explore the possibility of such scenarios, precise DFT calculations of the band structure were performed, revealing the contribution of Ce $4f$ electrons to the states at the Fermi level. Thus the even-odd transition can take place in a triplet scenario at symmetry points of a BZ.

We report a fully self-consistent calculation of the complex renormalization by exchange interactions and hence the complete phase diagram of conventional $s$-wave superconductors with magnetic impurities as well as the related physical properties including the optical response. We show that a small amount of magnetic disorder can drive the system into a gapless superconducting state, where the single-particle excitation gap vanishes whereas the superconducting order parameter ${\mathrm{\Delta }}_0$ remains finite. In this phase, the linear optical conductivity exhibits a finite absorption over the low-frequency regime, particularly for photon energies below the conventional threshold $2|{\mathrm{\Delta }}_0|$, even at low temperatures, in sharp contrast to the gapped state. The nonlinear response, however, remains coherent and is dominated by the Higgs-mode dynamics rather than the gapless quasiparticle background. These findings reveal a fundamental distinction between dissipative single-particle excitations and coherent collective dynamics of the condensate, a feature likely general to other gapless superconductors, and introduce a fundamentally different detection scheme, using THz spectroscopy to probe the signatures of Shiba states.

Although the homotopy-knot theory has been utilized to implement effective topological classification for non-Hermitian systems, more profound physical implications underlying distinct knot or link topologies are yet to be fully elucidated. In this work, we propose a one-dimensional non-Hermitian four-band lattice model and map out its phase diagram according to the distinct link structures residing in the momentum space. The topological phase diagram is ascertained through a spectral winding number. Furthermore, we derive the exact analytic formula for the phase boundaries that delineate different link topologies. To explore the concrete physical implications of distinct link topologies, we investigate the many-body ground-state entanglement entropy for free fermions loaded on such non-Hermitian lattice in real space. It turns out that different link topologies imply different magnitudes of entanglement. Moreover, we show that the central charge $c$ extracted from systematic finite-size scaling of entanglement entropy provides effective description of the phase diagram of the link topology. Finally, we further confirm the phase boundaries for the topological phase transitions alternatively by numerical calculations of the many-body ground-state fidelity susceptibility. Our results showcase the direct connection between link topology and observable entanglement properties of non-Hermitian systems, offering a novel experimental route to characterize link topological phases via measurable quantum correlations. This work not only bridges the gap between abstract topological classification and real-space physical phenomena but also paves the way for engineering non-Hermitian topological systems with tailored entanglement, with potential implications for topological quantum information processing.