Unconventional superconductors have specific signatures in their magnetic properties, such as intrinsic magnetization at interfaces and around defects and fractional and multiquanta vortices, with much attention focused on heavy fermion and high-$T_{\mathrm{c}}$ superconductors. Here, we report the observation of highly anomalous magnetization in β-$\mathrm{PdB}{\mathrm{i}}_2$, a layered superconductor previously shown to exhibit a magnetic-field-induced transition from $s$-wave to nodal $p$-wave superconductivity at a transition field $H^{*}\sim 0.1T(H_{\mathrm{C}1}<H^{*}<H_{\mathrm{C}2})$. This transition is driven by the coupling between spin-polarized electronic bands and the in-plane magnetic field. In the unconventional phase (above $H^{*}$) we observe three striking features: strictly linear and nonhysteretic dc magnetization, a sharp drop in the ac susceptibility when the field is applied parallel to the $\mathit{ab}$ plane, and a pronounced anisotropy in the magnetic response between parallel and perpendicular field orientations. We show that these features are directly correlated with the expected transition to the nodal $p$-wave state and propose that the unusual magnetization behavior can be explained by a transition from a conventional vortex lattice in the low-field $s$-wave phase to a domain structure corresponding to spatial phase separation into superconducting ($p$-wave) and normal domains above $H^{*}$. Our work identifies experimental signatures of unconventional multiphase superconductivity, offering an insight into the magnetic-field response of nodal states.

Light-induced metastable phases are exotic, long-lived out-of-equilibrium states of matter. Optical control offers a powerful approach to engineering these phases, enabling dynamic tuning of their electronic and structural properties. Using time- and angle-resolved photoemission spectroscopy, we investigate the emergence of a metastable phase induced by a strong infrared pump in the charge-density-wave (CDW)-Mott insulator $1T\text{−}{\mathrm{TaS}}_2$. Furthermore, we demonstrate how its properties can be optically manipulated by varying the photoexcitation strength. A long-lived stabilization of the renormalized electronic band structure serves as a signature of the metastable phase. It displays a relaxed periodic lattice distortion (PLD) and primarily lattice-driven dynamics. The emergence of a new dispersive band in the vicinity of the Hubbard bands reveals the formation of a novel band structure unique to the metastable phase. Our pump-fluence-dependent studies reveal a threshold (incident) fluence $F_C\sim 1.3\mathrm{mJ}/{\mathrm{cm}}^2$ for inducing the metastable phase, above which the band renormalization continuously evolves with increasing fluence. For $F⩽$ 3.4 $\mathrm{mJ}/{\mathrm{cm}}^2$, stronger photoexcitation progressively drives the phase to higher energies, accompanied by a more relaxed PLD and reduced CDW amplitude. The properties of the metastable phase are strongly influenced by the transient dynamics at each fluence, and the associated fast timescales suggest that the intrinsic CDW amplitude mode remains unaffected by optical manipulation. These findings highlight the potential of optical control in tuning the properties of metastable phases in quantum materials, offering new insights into the manipulation of CDW systems and paving the way for future investigations in nonequilibrium phase engineering.

We provide an exact evaluation of the out-of-time correlation (OTOC) functions for the localized $f$-particle states in the Falicov-Kimball model within dynamical mean-field theory. Different regimes of quantum chaos and quantum scrambling are distinguished by the winding numbers of the block Toeplitz matrices used in the calculation. The similarities of these fermionic OTOCs and their logarithmic derivatives for time evolution with the OTOCs for quantum spin models with disorder are also discussed.

Magnetotransport measurements are a sensitive probe of symmetry and electronic structure in quantum materials. While conventional metals exhibit longitudinal magnetoconductivity that is even in a magnetic field ($B$) for small $B$, we show that magnetic materials which intrinsically break time-reversal symmetry (TRS) show an odd-parity magnetoconductivity (OMC), with a leading linear-$B$ response. Using semiclassical transport theory, we derive explicit expressions for the longitudinal and transverse conductivities and identify their origin in Berry curvature and orbital magnetic moment. Crystalline symmetry analysis shows that longitudinal OMC follows the same point-group constraints as the anomalous Hall effect, while transverse OMC obeys distinct rules, providing an independent probe of TRS breaking. In the large $B$ quantum oscillation regime, we uncover both odd- and even-$B$ contributions, demonstrating OMC beyond the semiclassical picture. Explicit calculations in valley-polarized gapped graphene show that OMC peaks near the band edges, vanishes in the band gap, and follows the temperature dependence of the magnetic order parameter. Our results explain the odd-parity magnetoresistance recently observed in magnetized graphene and establish OMC as a robust transport signature of intrinsic TRS breaking in metals.

We theoretically investigate the interplay between nonreciprocal hopping and artificial magnetic fields in hexagonal photonic analogs of graphene quantum dots with zigzag and armchair edges. We demonstrate that nonreciprocal coupling overcomes finite-size hybridization limits, inducing robust zero-energy modes in zigzag photonic analogs of graphene quantum dots (PGQDs) even at ultracompact sizes. For armchair PGQDs, such modes—typically absent in the Hermitian limit—emerge only when the nonreciprocity exceeds a threshold. We further show that a weak synthetic magnetic field suppresses the non-Hermitian skin effect by counteracting boundary accumulation. These findings reveal edge-dependent mechanisms for topological mode formation in non-Hermitian photonic quantum dots and offer potential strategies for device miniaturization and controlling light localization in synthetic gauge-field platforms.

Quantum devices require coherent coupling over macroscopic distances. Recently, resonances due to Klein tunneling and Andreev reflection states (KARS) have been observed in a naturally occurring p-n junction at the interface between $\mathrm{B}{\mathrm{i}}_2\mathrm{S}{\mathrm{r}}_2\mathrm{CaC}{\mathrm{u}}_2{\mathrm{O}}_{8+x}$ (BSCCO), a $\mathrm{high}\text{−}{T}_{\mathrm{c}}$ superconductor (HTS), and graphene. The resonances appear as conductance oscillations with gating. Here, we show coupling between the KARS in BSCCO-graphene-BSCCO devices of varying separation (L). The coupling is evidenced by a power-law decay of resonance period as L increases from tens of nanometers to microns. These results demonstrate the long-distance coupling of KARS cavities in graphene-HTS junctions. The length dependence seen in experiments is supported by single-particle spectral functions which show KARS are coupled by transport modes in graphene. The strong coupling between KARS in BSCCO-graphene-BSCCO devices showcases the possibility of HTS-graphene junctions for quantum circuits and unconventional Josephson junctions.

Utilizing the hierarchy of correlations in the context of a Fermi-Hubbard model, we deduce the presence of quasiparticle bound states at the interface between a Mott insulator and a semiconductor, as well as within a semiconductor–Mott–semiconductor heterostructure forming a quantum well. In the case of the solitary interface, the existence of bound states necessitates the presence of an additional perturbation with a minimal strength depending on the spin background of the Mott insulator. Conversely, within the quantum well, this additional perturbation is still required to have bound states while standing-wave solutions even exist in its absence.

We propose a four-band model describing the electron energy spectra near the Weyl points in the topological semimetals of the TaAs family (TaAs, TaP, NbAs, NbP). This model takes into account the fact that these Weyl points result from the band-contact lines which would exist in the mirror-reflection planes of these materials if the spin-orbit interaction were absent in them. Within this model, we obtain conditions for the existence of the Weyl points, determine their positions in the Brillouin zone, and derive the explicit formula for dispersion of the bands along the straight line connecting the two close Weyl points with opposite topological charges. Using NbP as an example, the values of the parameters defining the model spectrum are found. The obtained results show that for the semimetals of the TaAs family, the charge-carriers spectrum in the vicinity of the two close Weyl points can be analyzed without complex band-structure calculations.

The low-energy properties of transition metal oxides (TMOs) are governed by the electrons occupying strongly correlated $d$-orbitals that are hybridized with surrounding ligand oxygen $p$ orbitals to varying degrees. Their physics is thus established by a complex interplay between the transition-metal (TM)-ligand hopping $t$, charge transfer energy ${\mathrm{\Delta }}_{\mathrm{CT}}$, and on-site TM Hubbard repulsion $U$. Here, we study the spectral properties of a one-dimensional analog of such a $pd$ system, with alternating TM $d$ and ligand anion $p$ orbitals situated along a chain. Using the density matrix renormalization group method, we study the model's single-particle spectral function, x-ray absorption spectrum, and dynamical spin structure factor as a function of ${\mathrm{\Delta }}_{\mathrm{CT}}$ and $U$. In particular, we present results spanning from the Mott insulating (${\mathrm{\Delta }}_{\mathrm{CT}}>U$) to negative charge transfer regime ${\mathrm{\Delta }}_{\mathrm{CT}}<0$ to better understand the ground-state and momentum-resolved excited-state properties of these different regimes. Our results can guide new studies on TMOs that seek to situate them within the Mott-Hubbard/charge transfer insulator classification scheme.

Recent theoretical work highlighted the unique properties of superconducting altermagnets, including the wealth of topologically nontrivial phases as well as their potential uses in spintronic applications. Given that no intrinsically superconducting altermagnets have yet been discovered, we study here the possibility of superconducting order induced by the proximity effect from a conventional $s$-wave superconductor. Through symmetry analysis and microscopic modeling we find that interesting superconducting phases can indeed be proximity induced in a thin altermagnetic film provided that weak Rashba spin-orbit coupling is present at the interface. Surprisingly, the resulting superconductor is generically nodal with a mixed singlet/triplet order parameter and, importantly for applications, capable of generating spin-polarized persistent current. We propose a set of candidate heterostructures with low lattice mismatch suitable to probe these effects experimentally.

Unraveling light induced ultrafast dynamics in three-dimensional Dirac materials is crucial for deepening our fundamental understanding and for advancing potential optoelectronic applications. While time-resolved pump-probe spectroscopy has predominantly revealed carrier dynamics governed by Dirac fermion cooling and population inversion, the full picture of relaxation pathways remains incomplete. In this Letter, we identify a relaxation channel in these materials. Using strong terahertz (THz) field excitation combined with a near-infrared (NIR) probe, we detect a long-lived carrier population persisting on the nanosecond timescale. This extended lifetime suggests that carriers become trapped in defect states, leading to sub-band-gap absorption in the NIR and pointing to the significant role of defect-assisted relaxation in the carrier dynamics of Dirac semimetals.

We use unrestricted Hartree-Fock, density matrix renormalization group, and variational projected entangled-pair state calculations to investigate the ground-state phase diagram of the triangular-lattice Hubbard model at “half doping” relative to single occupancy, i.e., at fillings of $(1\pm \frac{1}{2})$ electrons per site. The electron-doped case has a nested Fermi surface in the noninteracting limit, and hence a weak-coupling instability toward density-wave orders whose wave vectors are determined by Fermi-surface nesting conditions. We find that at moderate-to-strong interaction strengths, other spatially modulated orders arise, with wave vectors distinct from the nesting vectors. In particular, we identify a series of closely competing, itinerant long-wavelength magnetically ordered states, yielding to uniform ferromagnetic order at the largest interaction strengths. For half-hole doping and a similar range of interaction strengths, our data indicate that magnetic orders are most likely absent.

Employing the state-of-the-art time-dependent variational principle (TDVP) algorithm, we compute the spectra of charge-neutral excitations in a $\nu =1/2$ (bosonic) and $1/3$ (fermionic) fractional Chern insulator (FCI) on the Haldane honeycomb lattice model. The magnetoroton visualized from the dynamic density structure factor acquires a minimum gap at finite momentum that can go soft with increasing interaction and give rise to a charge density wave (CDW) at the same wave vector. As the system approaches the FCI-to-CDW transition point, we observe a pronounced sharpening of the roton mode, suggesting that the magnetoroton behaves more as a quasiparticle as it softens. Notably, this occurs while the single-particle gap remains finite. Besides the magnetoroton at finite momentum, we also construct quadrupolar chiral operators in a discrete lattice and resolve the chiral graviton mode around the $\mathrm{\Gamma }$ point of the Brillouin zone. Furthermore, we show the different chiralities of the gravitons of FCIs with opposite-sign Hall conductance. Our results offer clear spectral observations of the magnetoroton and chiral graviton in FCI lattice models. Our real-space approach paves the way for the tensor-network and quantum Monte Carlo study of the chiral graviton mode.

In two-dimensional lattice systems, massless Dirac fermions undergo doubling, leading to the cancellation of net chirality. We demonstrate that the recently discovered altermagnetism can induce a unique mass term, the altermagnetic mass term, which gaps out Dirac cones with one chirality while maintaining the other gapless, leading to the emergence of net chirality. The surviving gapless Dirac cones retain identical winding numbers and exhibit the quantum anomalous Hall effect in the presence of a trivial constant mass term. When subjected to an external magnetic field, the altermagnetic mass induces Landau level asymmetry in Dirac fermions, resulting in fully valley-polarized quantum Hall edge states. Our findings reveal that Dirac fermions with an altermagnetic mass harbor rich physical phenomena warranting further exploration.

Understanding how different structural phases interact differently (and/or similarly) with finite electric displacement D fields is of fundamental importance in determining the phase stability and field-induced properties, but little knowledge is known. Using a combination of analytic formulation and first-principles calculations, we investigate how different structural phases in ferroelectric Lithium Niobate (${\mathrm{LiNbO}}_3$) interact with finite D fields. Three important (low-energy) structural phases are considered, which include the polar TO phase caused by soft transverse-optic (TO) phonon, the LO phase caused by soft longitudinal-optic (LO) phonon, and the nonpolar (nonP) phase. Our results reveal several key outcomes: (i) Different structural phases display interesting (and notably different) free-energy landscapes when they interact with finite D fields. While the LO phase exhibits dual free-energy minima at low D fields, the TO phase shows only a single free-energy minimum. (ii) The LO and TO phases show drastically different field-induced tunability of polarization. The polarization of the TO phase alters dramatically with the D field. In contrast, the polarization of the LO phase shows an unusual resistance to the D field. (iii) A pronounced phase transition is discovered in ${\mathrm{LiNbO}}_3$ under finite D fields (in which the solid transforms from a nonpolar phase to the polar TO phase), and the critical D field is determined to be 0.07 ${\mathrm{C}/\mathrm{m}}^2$. The phase transition is found to be second order, and the free-energy barrier of phase transformation is shown to depend on the D field significantly. The physical origin underlying the profound differences in the field-induced responses between the LO and TO phases is provided, and is revealed to be dictated by the mode effective charge.

Antiferroelectric materials, characterized by their unique antiparallel spontaneous polarization patterns, have garnered significant interest as promising candidates for next-generation energy storage applications. Among these materials, ${\mathrm{PbZrO}}_3$ (PZO) has been extensively studied as a model system. A variety of domain wall configurations have been proposed. However, atomic-scale studies of domain walls have been limited in the image plane. Here, we show that the three-dimensional (3D) configuration of the translational boundaries in PZO can be revealed using multislice electron ptychography with adaptive propagator, which allows for depth-resolved imaging of domain wall structures. The 3D structure of domain walls at the atomic scale is likely intricately linked to local variations in chemical composition, polarization, and even conductivity, presenting novel and promising directions for future studies.

Dirac cones featuring linearly tilted band diagrams can be classified into type I, II, and III based on their degree of tilting. Type-III Dirac cones combining flat and linear dispersion have been largely unexplored in the acoustic domain. The Mielke model stands out as a potential candidate for supporting type-III Dirac cones. However, an experimentally feasible scheme for realizing the Mielke model still remains elusive. Here, we propose an acoustic implementation of the staggered Mielke model, which hosts type-III Dirac cones arising from flat band. By tuning onsite staggered frequency, we demonstrate the emergence, movement, and merging of these type-III Dirac cones at the Brillouin-zone boundary. We also observe exotic edge states connecting the type-III Dirac cones in the acoustic metamaterial. These results pave the way for experimentally investigating type-III acoustic Dirac cones and examining their behaviors, and thus set a new paradigm for manipulation of acoustic waves.

$\mathrm{Cr}{X}_3$ ($X$ = Cl, Br, I) have the same crystal structure and Hamiltonian but different ligand spin-orbit coupling (SOC) constant ${\lambda }_X$, providing an excellent material platform exploring for exotic two-dimensional (2D) spin orders. Their microscopic mechanism underlying 2D spin physics remain unestablished, along with experimental corroboration of Kitaev exchange interaction, central to realizing topological quantum spin liquids. Finding direct evidence for Kitaev interaction and determining its value has been an essential but formidable challenge in Kitaev physics. Here we report the direct Kitaev interaction signature in magnetic anisotropy measured by ferromagnetic resonance (FMR) spectroscopy. We present measured values of Heisenberg $J$, Kitaev $K$, and off-diagonal symmetric $\mathrm{\Gamma }$ exchange interactions in $\mathrm{Cr}{X}_3$ determined using FMR and exact diagonalization. $K$ and $\mathrm{\Gamma }$ exhibit dominant dependencies on ${\lambda }_X$, indicating its central role in 2D magnetism. Our study provides a foundation for designing 2D magnetic materials exhibiting novel behaviors by tuning intrinsic material parameters such as SOC.

A magnonic waveguide based on a domain wall (DW) is considered to be a crucial breakthrough toward the realization of magnonic nanocircuits. However, the effective control of spin waves propagating in DWs remains to be explored. Here, we construct a magnonic crystal (MC) by using a chain of the domain wall skyrmions (DWSKs) to manipulate the spin-wave propagation in DWs. We show that the DWSK chain can be created by leveraging the voltage-controlled Dzyaloshinskii-Moriya interaction. The DWSK-based MC opens magnonic band gaps, which can be dynamically adjusted through magnetic fields modulating the DWSK size. Furthermore, the manipulation of spin waves by the DWSK-based MC remains robust in curved DWs, demonstrating its adaptability to complex device architectures. Our work provides an effective method to control the spin-wave propagation in DWs, and it paves the way for designing energy-efficient magnonic nanocircuits.

While ferromagnetism and antiferromagnetism are well-established classes of magnetic order, a third class of collinear magnetic order, termed altermagnetism, has recently attracted scientific interest. We measured magnetic circular dichroism (MCD) in core-level photoemission (XPS) at the Ru $2p_{3/2}$ and $2p_{1/2}$ core levels in epitaxial ${\mathrm{RuO}}_2\left(110\right)/{\mathrm{TiO}}_2\left(110\right)$ films using circularly polarized x rays at 6 keV, as well as x-ray magnetic circular dichroism (XMCD) in resonant x-ray absorption at the Ru ${\mathrm{M}}_{3,2}$ ($3p_{3/2}$ and $3p_{1/2}$) edges. Charge transfer multiplet calculations show that the MCD-XPS and the XMCD can be explained by an altermagnetic locking of Ru magnetic moments and a distorted crystal field orientation. The distortion is caused by the epitaxial strain. The collinear magnetic moments in ${\mathrm{RuO}}_2$ occupy sublattice sites with distorted octahedral crystal fields that are rotated by ${90}^{\circ }$ with respect to each other. A change in the sign of the MCD-XPS at different sample positions indicates the presence of altermagnetic domains with the size of around hundreds of micrometers.