Recent discovery of the superconducting ground state in systems lacking perfect periodicity but with long-range ordering has opened up an exciting new avenue for superconductivity based on aperiodic systems. In this work, we explore the scope by theoretically investigating the behavior of the superconducting order parameter (OP) in aperiodic binary systems (ABSs), both Fibonacci and non-Fibonacci type, based on the attractive Hubbard model. We begin with a one-dimensional toy model, and for the generality of our findings, we extend our analysis to two-dimensional ABSs. Remarkably, despite the increased dimensionality, the qualitative features of the OP remain largely preserved. By systematically analyzing models generated through various growth rules, we elucidate the influence of aperiodicity on the OP amplitudes and how it evolves towards the periodic limit with the change in the structural pattern. We study the evolution of the OP with respect to the temperature, strength of the interaction, and nearest-neighbor hopping amplitude. Our numerical analysis identifies the most favorable ABS and parameter regime that support enhanced onsite pairing amplitudes. Additionally, we provide a comparative analysis of the superconducting transition temperatures across the range of aperiodic configurations. To gain further insight into these systems, we compute key thermodynamic quantities: the entropy and electronic specific heat, and examine their dependence on the underlying structural sequences. This analysis enables us to determine which ABSs are most conducive to Cooper pair formation.

Polar topological structures in perovskites offer promising routes toward next-generation nonvolatile memory and logic devices, yet thermally stable, lead-free, and electrically controllable systems remain rare. Here, by applying machine-learning interatomic potentials and high-throughput screening of over 1300 candidate compounds, we report the emergence of an in-plane polar vortex-antivortex state in ${\mathrm{BiAlO}}_3/{\mathrm{BiGaO}}_3$ superlattices, where each constituent is collinearly (anti)polarized. The vortex topology is found to be stabilized by cooperative coupling between polarization and octahedral rotations. This vortex phase remains the stable ground state up to 900 K and exhibits enhanced stability against deforming electric fields than the typical ${\mathrm{PbTiO}}_3/{\mathrm{SrTiO}}_3$ system. Global electric fields reversibly switch the system between the vortex state and a ferroelectric state. Localized biases write and erase stable nanoscale vortex bits with nonvolatile retention and clear spatial addressability. The presently discovered platform provides a promising route toward advanced storage devices.

The non-Hermitian skin effect is an intriguing phenomenon that initially emerges in non-Hermitian systems featuring nonreciprocal hoppings. In such settings, eigenstates tend to accumulate predominantly at one end of the lattice chain under open boundary conditions. However, the localization length of these skin states remains fixed and is independent of the lattice size. Here, we demonstrate a distinct type of skin effect in a coupled four-layer Hatano-Nelson model, where the localization length scales inversely with the lattice size, even in the presence of weak interlayer coupling. Notably, we find that every two chains sharing the same complex potentials form identical loops in the complex energy plane. Moreover, all eigenstate profiles are antisymmetrically distributed across two pairs of double chains, provided their nonreciprocal hoppings are opposite in direction. Our results reveal that scale-free skin effects can be engineered by both on-site potentials and nonreciprocity, offering new avenues for exploring scale-free skin effects in multichain non-Hermitian systems.

We study disorder effects in the extended Su-Schrieffer-Heeger model using a convolutional neural network (CNN) trained on reduced correlation matrices (RCMs) of disorder-free systems to predict winding number phase diagrams in systems with off-diagonal and diagonal disorder. The trained CNN model generalizes to a chiral-symmetry-preserving off-diagonal disorder system, but fails in the presence of a chiral-symmetry-breaking diagonal disorder system. Using principal component analysis of the RCM feature space, we demonstrate that disorder-free and symmetry-preserving systems share overlapping feature manifolds, whereas symmetry-breaking disorder causes them to diverge. Inverse participation ratio (IPR) and energy-spectrum analyses further demonstrate that off-diagonal disorder preserves topological edge states, whereas diagonal disorder drives a transition to an Anderson insulator. Our results show that the out-of-distribution behavior of a CNN trained on clean systems can be understood through the evolution of the RCM feature space under symmetry-preserving and symmetry-breaking disorder, with IPR and energy-spectrum analyses providing the corresponding physical interpretation.

The Eigenstate Thermalization Hypothesis explains thermalization in isolated quantum systems through the statistical properties of observables in the energy eigenbasis. We study the crossover from integrability-to-chaos in the spin-$1/2$ XXZ chain by introducing a local perturbation. Using exact diagonalization, we characterize this crossover through spectral correlations, standard ETH indicators, and eigenstate entanglement entropy. Beyond these conventional probes, we introduce a submatrix-based framework in which local observables are projected onto contiguous energy windows along the diagonal of their representation in the Hamiltonian eigenbasis. The resulting real-symmetric submatrices exhibit a banded matrixlike structure and display both short-range and long-range spectral correlations similar to those of the Hamiltonian. Remarkably, this resemblance between the spectral statistics of the Hamiltonian and those of the submatrices persists even in intermediate regimes that are not fully chaotic, suggesting that signatures of the integrability-to-chaos crossover are reflected in collective correlations among observable matrix elements, even when the system is not fully ergodic.

The spectral form factor (SFF) is a measure of energy correlations and has been widely used to identify the transition from the ergodic to the localized phase in interacting many-body quantum systems. In this work, we show that in a disordered Heisenberg spin-$\frac{1}{2}$ model, the finite temperature SFF can be used to generate a canonical phase diagram exhibiting a critical temperature $T_{\mathrm{MBL}}$. Using simple ideas of statistical mechanics, we obtain the critical energy density ${\epsilon }_{\mathrm{MBL}}$ dual to $T_{\mathrm{MBL}}$. We show that the mobility edge, numerically estimated from the spread of local perturbations and the optical conductivity, indeed coincides with ${\epsilon }_{\mathrm{MBL}}$.

In this work, we study one-dimensional interacting non-Hermitian quasiperiodic lattices with asymmetric power-law hopping in the presence of time-reversal symmetry (TRS). In contrast to earlier works on short-range non-Hermitian quasiperiodic models with TRS, both with and without interactions, where the spectral, delocalization-localization, and topological transitions have been identified to coincide, we show that in this setting, the reality of the many-body eigenspectrum does not necessarily indicate a topologically trivial non-Hermitian many-body localization (NHMBL) regime. Instead, we uncover a topologically trivial intermediate regime in which the states are primarily multifractal, and the spectrum remains fully real, thereby leading to the restoration of TRS of the eigenstates before the system crosses over into the NHMBL phase. Within this regime, interactions qualitatively reshape the noninteracting phenomenology, i.e., it destroys the single-particle mobility and multifractal edges of the noninteracting counterpart and rather generates many-body edges separating localized and extended states, comprising of both ergodic and nonergodic ones. Furthermore, we unveil that due to the long-range nature of the asymmetric hopping, the entire topologically nontrivial ergodic phase under periodic boundary conditions does not generically map to boundary-localized skin modes under open boundary conditions. Whenever skinlike states occur, they are indeed many-body scale-free localized in nature. These unconventional phases and crossovers are corroborated by the long-time dynamics of local observables and density imbalance. Our results thus demonstrate that the interplay of interactions and long-range hopping in non-Hermitian quasiperiodic systems gives rise to a modified understanding of interconnections between the various phases that goes beyond the standard paradigm established for short-range non-Hermitian quasiperiodic models.

We propose a protocol to tailor dynamical quantum phase transitions (DQPTs) by double-mode squeezing onto the initial state in the $\mathit{XY}$ chain. The effect of squeezing depends critically on the system's symmetry and parameters. When the squeezing operator breaks particle-hole symmetry (PHS), DQPTs become highly tunable, allowing one to either induce transitions within a single phase or suppress them. Remarkably, when PHS is preserved and the squeezing strength reaches $r=\pi /4$, a distinctive class of DQPTs emerges, independent of the quench path. This distinction is characterized by two key features: (i) the collapse of all Fisher zeros onto the real-time axis, and (ii) the saturation of intermode entanglement to its maximum in each $(k,-k)$ mode. Moreover, the critical momenta governing the DQPTs coincide exactly with the modes attaining the maximal entanglement. At this distinctive point, the dynamical phase vanishes, leading to a purely geometric evolution marked by $\pi$ jumps in the Pancharatnam geometric phase. Our work establishes initial-state squeezing as a versatile tool for tailoring far-from-equilibrium criticality and reveals a direct link between entanglement saturation and nonanalytic dynamics.

Chiral phonons endow lattice vibrations with angular momentum and can give rise to phonon magnetism, offering routes to control magnetism and topology. However, experimentally resolving their polarization, handedness, and magnetism across the Brillouin zone remains challenging. Here, we formulate a measurement-oriented inelastic neutron scattering (INS) framework to diagnose these attributes from the nuclear one-phonon response in the scattering readout. We demonstrate that angular intensity fingerprints classify linear, elliptical, and circular polarizations, while phase-sensitive time-resolved signatures provide a benchmark readout of handedness. Furthermore, we show that phonon magnetic moments manifest as characteristic spectral splittings and intensity redistributions under external fields. Benchmarked in chiral Te and paramagnetic ${\mathrm{CeF}}_3$, this framework provides a comprehensive momentum-resolved probe for the geometric and magnetic nature of chiral phonons.

The search for high-performance thermoelectrics is increasingly focused on quasi-one-dimensional (Q-1D) materials, which leverage quantum confinement effects to intrinsically decouple transport properties. Herein we report a series of Q-1D phosphidosilicates with systematically tunable structural distortions, stereochemically active lone pairs, anharmonic chains, and distinct bonding hierarchies. This unique structural combination induces strong phonon anharmonicity, resulting in intrinsic ZT values above 1, including a peak of $\sim 2.32$ along the $a$ direction in $\mathrm{B}{\mathrm{a}}_4{\mathrm{Si}}_3{\mathrm{P}}_8$. Quantifying the influence of structural distortion reveals two distinct trends. Electronically, increased distortion promotes valley convergence and drives bands toward degenerate Q-1D flat bands, enhancing power factors. This effect is most pronounced in $\mathrm{C}{\mathrm{a}}_3{\mathrm{Si}}_2{\mathrm{P}}_4$, which exhibits superior carrier mobility and high power factor under both doping types, matching state-of-the-art NbFeSb. Phononically, $\mathrm{C}{\mathrm{a}}_3{\mathrm{Si}}_2{\mathrm{P}}_4$ exhibits a lattice thermal conductivity nearly three times higher than ${\mathrm{K}}_2\mathrm{Si}{\mathrm{P}}_2$ despite its heavier and more complex structure, violating conventional Slack's rule. Moreover, structural complexity shifts thermal transport toward wavelike behavior, culminating in $\mathrm{B}{\mathrm{a}}_4{\mathrm{Si}}_3{\mathrm{P}}_8{}^{\prime }\mathrm{s}$ ultralow phonon conductivity without nanostructuring. These phosphidosilicates demonstrate how structural distortion can simultaneously suppress thermal transport and enhance electronic performance via dimensional tailoring, offering a promising platform for advanced thermoelectrics.

This study systematically investigates the lattice thermal transport properties of layered ternary chalcogenides ${X\text{Sc}Y}_2$ ($X$ = Li, Na; $Y$ = Se, Te) using a unified thermal transport theory that combines self-consistent phonon calculations with the Wigner transport equation. An anomalous mass effect is first identified, where the lighter ${\mathrm{LiScTe}}_2$ exhibits a lower particle-like thermal conductivity (${\kappa }_{\mathrm{p}}$) than ${\mathrm{NaScTe}}_2$, originating from enhanced low-frequency anharmonicity associated with weakened Sc–Te bonding, acoustic–optical coupling, and enlarged phonon gaps. Beyond this particle-like picture, we uncover a distinct high-frequency mechanism governing cross-plane heat transport. Cross-gap hybridization enhances the Born effective charges, reinforcing lattice anharmonicity, while the rattling of light Li ions together with a large phonon band gap induces strong high-frequency phonon scattering, particularly four-phonon scattering, resulting in pronounced phonon linewidth broadening that significantly enhances wave-like coherent phonon transport (${\kappa }_c$) along the out-of-plane direction. Consequently, in ${\mathrm{LiScTe}}_2$ at 700 K, ${\kappa }_c$ contributes nearly 50% of the total lattice thermal conductivity ${\kappa }_L$ and becomes dominant at higher temperatures. As a result, the anomalous mass effect breaks down along the out-of-plane direction at elevated temperatures, despite persisting in plane. Incorporating ${\kappa }_c$ leads to good agreement between calculated and experimental ${\kappa }_L$ for ${\mathrm{NaScTe}}_2$ and ${\mathrm{NaScSe}}_2$. These findings highlight the critical role of rattling-induced high-order anharmonicity and coherent phonon transport in governing cross-plane heat transport in layered systems.

A clear understanding of the physics of complex magnetic oxides is crucial for unlocking new pathways to design novel materials for technological applications. We present here a detailed investigation of the temperature- and magnetic-field-driven magnetic evolution of $\mathrm{BaErFe}{\mathrm{O}}_4$ using a suite of complementary techniques, including neutron diffraction, Mössbauer spectroscopy, $\text{dc}$ magnetization, and transverse susceptibility measurements. Below $T_{\mathrm{N}1}\approx 50\mathrm{K}$, the Fe sublattice orders into an incommensurate collinear spin-density-wave state with propagation vector $k_1=\left(0,0,\sim 0.4\right)$. The $3d-4f$ exchange coupling drives a transition at $T_{\mathrm{N}2}\approx 32\mathrm{K}$ to a commensurate noncollinear antiferromagnetic phase characterized by $k_2=\left(0.5,0,0.5\right)$ involving ordering of both $\mathrm{F}{\mathrm{e}}^{3+}$ and $\mathrm{E}{\mathrm{r}}^{3+}$ ions, followed by a further modification of the Er magnetic configuration below $T_{\mathrm{N}3}\approx 5\mathrm{K}$ governed by dominant $4f-4f$ interactions. Strong geometrical frustration prevents complete long-range magnetic ordering, leaving a substantial fraction of spins in a short-range correlated state that serves as a metastable template for phase separation. Under an applied magnetic field of ${\mu }_{0}H\approx 0.2\mathrm{T}$, the $\mathrm{E}{\mathrm{r}}^{3+}$ spins within these regions undergo a metamagnetic spin-flip transition, nucleating ferromagnetic clusters. This metamagnetic response remains fully reversible down to 8 K, while a crossover to an irreversible ferromagneticlike regime occurs at lower temperatures, attributed to kinetic arrest of the magnetic clusters. A complex field-induced phase separation is established, in which ferromagnetic clusters of distinct populations coexist with the long-range antiferromagnetic order of the Er sublattice. These findings underscore the complex interplay among magnetic anisotropy, magnetic frustration, and quenched disorder in stabilizing the magnetic ground state of $\mathrm{BaErFe}{\mathrm{O}}_4$.

We introduce ${\mathrm{Bi}}_2{\mathrm{CuO}}_3$(${\mathrm{SO}}_4$) as a rare example of a spin-ladder magnet with ferromagnetic interactions on the rungs. Its magnetic response is studied through measurements of temperature-dependent magnetic susceptibility and heat capacity, field-dependent magnetization, and electron spin resonance spectroscopy. These experiments are complemented by density-functional-theory calculations combined with the construction of maximally localized Wannier functions and an analysis of the relevant superexchange pathways. Quantum Monte Carlo simulations are employed to model thermodynamic properties and to quantitatively determine the magnetic exchange parameters. Our combined approach identifies ${\mathrm{Bi}}_2{\mathrm{CuO}}_3$(${\mathrm{SO}}_4$) as a two-leg spin-ladder system with ferromagnetic rungs ($J^{\prime } \approx -208\mathrm{K}$) and antiferromagnetic legs ($J\approx 258\mathrm{K}$). These interactions of similar magnitude arise from remarkably different superexchange pathways, with the Cu–Cu distance along the leg being almost twice as long as the respective distance along the rung. The antiferromagnetic leg coupling represents the strongest oxygen-mediated long-range superexchange in a ${\mathrm{Cu}}^{2+}$ compound and sets a benchmark for the role of complex superexchange pathways in quantum magnets.

$\mathrm{N}{\mathrm{i}}_{2-x}\mathrm{C}{\mathrm{o}}_x\mathrm{ScSb}{\mathrm{O}}_6$ solid solutions ($x=0.1$, 0.2, 0.3, 0.4) have been studied by magnetization and neutron powder diffraction measurements. All samples are magnetically ordered below $T_{\mathrm{C}}\approx 63\mathrm{K}$ and metamagnetic transitions are observed at fields $\sim 2.5$ T at 2 K. Neutron diffraction shows that the metamagnetic transition marks a $k$-flop from helical wave vector $\mathit{k}=\left[00k_z\right]$ to cycloidal $\mathit{k}=\left[k_{x}00\right]$ spin spirals, and the latter gradually transform to a coexisting ferrimagnetic $\mathit{k}=\left[000\right]$ state at higher field. Fractional values of $k_z$ and $k_x$ are consistent with complete devil's staircase behavior, driven by locking-in of spins to easy-axis directions in the $ab$-plane that stabilizes commensurate $6p/q$ wave vectors ($p, q=\mathrm{integers}$).

High-entropy perovskites offer a unique platform for exploring magnetic phenomena arising from extreme $B$-site chemical disorder. In $\mathrm{Sm}\left(M7\right){\mathrm{O}}_3$, where there are seven cations in equal amounts at the $B$ site ($M=\mathrm{Ti}$, Cr, Mn, Fe, Co, Ni, Cu), we observe long-range antiferromagnetic ordering near 105 K accompanied by a small but robust excess magnetic moment intrinsic to the chemically disordered lattice. This uncompensated moment is evident from zero-field-cooled – field-cooled irreversibility, shifts in the isothermal $M$($H$) loops, and discrete remanent states identified through direct-current–demagnetization measurements. Remarkably, cooling fields as small as $\pm 20$ Oe are sufficient to select the direction of the excess moment, and the chosen magnetic state remains stable against applied fields up to 50 kOe. A low-temperature anomaly in the remanent magnetization further reveals a secondary contribution from the $\mathrm{S}{\mathrm{m}}^{3+}$ sublattice, although the primary origin of the excess moment resides in the $B$-site antiferromagnetic sublattice.

When magnon propagates through a magnetic texture, the Hall effect arises as a prominent feature to characterize the underlying nontrivial magnetic topology, due to the action of the emergent pseudomagnetic field. Here, we propose a complementary framework based on the angular momentum conservation, which offers an intuitive yet quantitative toolkit to analyze the magnon deflection. Specifically, the spin and orbital components of the angular momentum carried by the magnon, as well as its redistribution along magnon trajectories are anatomized. Guided by the intrinsic constraint of angular momentum conservation, the magnon Hall angle is evaluated through the associated geometric features of the magnon trajectories.

The origin of stripe-domain (SD) formation in soft magnetic thick films remains unresolved, particularly in NiFe-based systems where SDs are often associated with columnar microstructure. Here, by combining fixed-thickness processing control, decisive reference samples, quantitative structural and magnetic analysis, and micromagnetic validation, we show that the experimentally determined effective anisotropy is the key controlling factor for SD formation. Columnar, microstructure in NiFe films is identified as an important, but nonunique, structural route for generating or enhancing this anisotropy. A pressure-tuned 350-nm NiFe series traverses labyrinth-SD, SD, and in-plane-domain states at fixed thickness, whereas an annealed 200-nm NiFe series exhibits systematic stripe broadening without a change in thickness. These data are complemented by an amorphous FeCoHf SD film and a 130-nm-thick columnar NiFe film without SDs. These two reference samples demonstrate that columnar microstructure is neither necessary nor sufficient for SD formation. Stripe-bearing and stripe-free states are separated more clearly by the experimentally determined effective anisotropy scale than by the mere presence of columnar geometry. Within the columnar NiFe family, the aspect ratio $h/w$ provides a useful structural proxy for stripe stabilization, and stripe broadening is quantitatively associated with reduced effective anisotropy. Minimal micromagnetic simulations reproduce both the shift of the SD-IP phase boundary and the increase in stripe period under reduced perpendicular anisotropy. We conclude that SD formation is governed by a processing-defined effective anisotropy landscape, within which columnar microstructure is an important structural route but not a universal prerequisite for stabilization.

Polar antiferromagnetic metals have recently attracted increasing interest due to their combined traits of both ferromagnets (with spin polarization) and antiferromagnets (absence of net magnetization) for spintronic applications. However, the inherently incompatible nature of antiferromagnetism, metallicity, and polarity pose a significant challenge in designing these materials. Herein we propose that charge disproportionation can lead to this novel state in the negative charge transfer gap regime in molecular orbital crystals. As a proof of concept, this proposal is demonstrated by molecular orbital analyses of first-principles density functional theory plus $U$ electronic band structures for the representative Ruddlesden-Popper bilayer perovskite oxide ${\mathrm{Sr}}_3{\mathrm{Co}}_2{\mathrm{O}}_7$, corroborated by density matrix renormalization group calculations. Due to the negative charge transfer nature of ${\mathrm{Co}}^{4+}$ and strong interlayer coupling, localized molecular orbitals stemming from the hybridization of Co $d_{z^2}$ and $d_{xz/yz}$ orbitals through the apical oxygen $p$ orbitals preferentially emerge within each bilayer unit and develop antiferromagnetic ordering by invoking Hubbard repulsion. Charge disproportionation driven by Hund's physics causes an occupation imbalance (with broken inversion symmetry) in the remaining $d_{xy}$ and $d_{x^2-y^2}$ orbitals from distinct Co atoms within the bilayer unit, resulting in the polar metallicity. Meanwhile, this charge disproportionation scenario allows consequent conducting carriers to couple with interlayer local spins via Hund's coupling, giving rise to in-plane double-exchange ferromagnetism. Our molecular orbital formulation further provides a guide towards an effective Hamiltonian for modeling the unconventional synergy of metallicity, polarity, and antiferromagnetism in ${\mathrm{Sr}}_3{\mathrm{Co}}_2{\mathrm{O}}_7$, which may be a unified framework widely applicable to double-layer Ruddlesden-Popper perovskite oxides.

Three-dimensional (3D) curvilinear nanomagnetism is an emerging field that has gained attention owing to modern advances in material engineering. Current experimental techniques now enable the fabrication of intricate ferromagnetic systems with 3D geometries, where curvature can induce asymmetry in magnon propagation and ultrafast chiral domain-wall dynamics. This paper reports on the formation and stability of conical-helix magnetic textures in thin ferromagnetic cylindrical nanotubes with interfacial Dzyaloshinskii-Moriya interaction (DMI) and radial magnetic anisotropy. It is found that geometry imposes a natural quantization of the helix wavelength along the azimuthal direction. The sign of the DMI strength ($D$) dictates the preferred handedness of the magnetization around the tube's circumference, leading to a notable asymmetry in the nucleation modes with respect to $D=0$, a curvature effect particularly pronounced at smaller radii. Finite-element micromagnetic simulations support the analytical predictions, showing how the magnon instability of the saturated state, in which the frequency of a particular mode vanishes at a critical field, correlates to the nucleation of the predicted magnetic textures at those fields. These findings provide guidelines for tailoring helical textures in ferromagnetic nanotubes with defined chirality, offering experimentally testable predictions for applications in spintronics, and a framework that can be extended to more complex curved three-dimensional magnetic nanostructures.

Interfacial magnetism in complex oxide heterostructures underlies both fundamental many-body physics and advanced spintronic applications. Here we report a pronounced stacking-order dependence of magnetic coupling in $\text{L}{\text{a}}_{0.78}\text{C}{\text{a}}_{0.22}\text{Mn}{\text{O}}_3/\mathrm{SrRu}{\mathrm{O}}_3$ (LCMO/SRO) bilayers. While Ru–O–Mn superexchange drives antiparallel spin alignment between interfacial Ru and Mn moments, macroscopic antiferromagnetic correlations emerge only within a proper thickness ratio range, consistent with first-principles calculations. Ferromagnetic enhancement—manifested as a significant increase in Curie temperature ($T_{\mathrm{C}}$)—occurs exclusively when LCMO is grown atop SRO, vanishing in the inverse stack. Atomically resolved structural analysis attributes this unidirectional phenomenon to suppressed Jahn-Teller distortions and preferential in-plane orientation of the LCMO crystallographic $c$ axis in the LCMO grown on SRO configuration, which together strengthen double-exchange interactions. Control experiments rule out interfacial charge transfer and Sr interdiffusion as primary mechanisms. These findings establish that stacking-sequence–induced structural asymmetry serves as a dominant control parameter for interfacial ferromagnetism, offering a deterministic route to engineer correlated oxide heterostructures.