We describe a case of instability of the paramagnetic order in an electron gas confined in a thin tubular semiconductor nanowire with a Rashba spin-orbit interaction. This situation is realized when, for a critical value of the Rashba coupling constant ${\alpha }_c$, dependent only on the radius of the tube, single-particle energies corresponding to opposite spin orientations along the direction tangent to the tube become equal. A theory of the magnetic phase transition considers the presence of the Coulomb interaction, evaluated within the Hartree-Fock approximation, which lifts the spin degeneracy and leads to the formation of quasiparticle states that support a continuous rotation of the electron spin in the momentum space along the axis of the wire. For a chemical potential localized within the gap between the quasiparticle states, the long-range magnetic order manifests macroscopically through a constant radial spin polarization proportional with the magnitude of the gap.

In a magnetic field, bilayer graphene hosts an octet of pseudo-zero-mode (PZM) electron levels nearly degenerate in orbitals $n=(0,1)$, valleys, and spins. They split in valleys by electrostatic gating. In gated bilayer graphene, in which the interlayer bias is set up to flip sign across a line, one has a line junction that traps a portion of PZM electrons inside the insulating bulk band gap, giving rise to electron states localized along the junction, known as kink states. A close look is made into the spectra and electromagnetic response of such kink states. There are two species of valley current associated with them, a drift current driven by the bias gradient and a circulating current coming from cyclotron motion. It turns out that they both flow in essentially the same direction, with the circulating current exhibiting a magnetic character distinct from those of other higher levels. In equilibrium, they spatially circulate within the kink states, creating a quasi-one-dimensional channel of orbital magnetization. The electric control of the orbital magnetization and valley currents via a network of gated junctions will find useful applications in valley electronics.

We study the ground-state phase diagram of the spin-$1/2$ Kitaev-Heisenberg model on the bilayer honeycomb lattice with large-scale tensor-network calculations based on the infinite projected entangled pair state (iPEPS) technique with the simple-update scheme, as well as high-order series expansions using perturbative continuous unitary transformations (pCUTs). We find that beyond various magnetically ordered phases, including ferromagnetic, zigzag, antiferromagnetic (AFM), and stripy states, two extended quantum spin liquid phases arise in proximity of the Kitaev limit. While these phases also appear in the monolayer Kitaev-Heisenberg model, our results further show that a valence bond solid (VBS) phase emerges in a relatively narrow range of parameter space between the AFM and stripy states. This VBS state can be adiabatically connected to isolated Heisenberg dimers. Our results highlight the importance of interlayer interactions on the emergence of quantum phases in the bilayer Kitaev materials.

We investigate the quantum phase diagram of an “odd” variant of the two-dimensional Ising Fradkin-Shenker model, characterized by a uniform background of static $e$ and $m$ charges. Using large-scale tensor network and exact diagonalization methods, we determine the topology of the phase diagram, identifying an “odd” deconfined phase, confinement- and Higgs-induced valence bond solids (VBS), and a trivial paramagnet. Most notably, we uncover an exotic multicritical point along the self-dual line, where electric and magnetic excitations are related by an enriched ${\mathbb{Z}}_2$ duality. This transition is marked by the simultaneous onset of confinement, Higgs condensation, translational symmetry breaking, and spontaneous duality symmetry breaking. Within our numerical accuracy, the transition appears continuous, involving the softening of excitation gaps for $e$ and $m$ anyons at finite momentum. At intermediate couplings, we further identify VBS phases with enlarged unit cells, potentially indicating frustration-induced crystalline order beyond commensurate limits.

Three-dimensional topological semimetals like type-II Weyl semimetal transition metal dichalcogenides $(T_d{\text{-WTe}}_2 \text{and} {\mathrm{MoTe}}_2)$ exhibit intriguing phenomena associated with various symmetries governing their band structure. Density functional theory-based band structure calculations and angle-resolved photoemission spectroscopy studies on $T_d{\text{-WTe}}_2$ have showcased the temperature-dependent variation of chemical potential and Fermi surface modifications. In this work, the decisive role of the complex band dispersion and Fermi surface topology changes (FSTCs) of ${\mathrm{WTe}}_2$ in modulating the scattering channels for charge carriers has been studied using low-frequency resistance noise spectroscopy, a transport-based probe extremely sensitive to disorder dynamics and charge carrier interference. A nonmonotonic dependence of noise with temperature is observed, with noise peaks close to temperatures associated with FSTCs in $T_d{\text{-WTe}}_2$ due to disappearance of specific carrier pockets in the Fermi surface. The time reversal symmetry in the spin-textured band structure of ${\mathrm{WTe}}_2$ is broken in a finite magnetic field leading to the emergence of additional scattering channels for the charge carriers that influence the resistance noise and the scattering timescales.

We investigate the evolution of conductance quantization and subband structure in a weakly confined quasi-one-dimensional channel as a function of carrier density and perpendicular magnetic field. As the carrier density is reduced, the $2e^2/h$ plateau is progressively suppressed and an avoided crossing develops between the lowest two subbands in transconductance, indicating a strong intersubband coupling. This behavior is consistent with an interaction-driven restructuring of the electron system into a zigzag or two-row configuration in the regime of dominant Coulomb interactions. The application of a perpendicular magnetic field suppresses the anticrossing through enhanced magnetoelectric confinement, which reduces inter-row tunneling and hybridization via magnetic compression of the wave function. At intermediate fields ($\sim 0.5\mathrm{T}$), further reduction of carrier density leads to the emergence of the $0.7(2e^2/h)$ feature coexisting with the restored $2e^2/h$ plateau. In addition, spin-split features, such as $1.5(2e^2/h)$, begin to resolve in higher subbands in the low-density, weakly confined regime. At higher fields ($\sim 0.7\mathrm{T}$), where the anticrossing is fully quenched, the low-density regime exhibits the coexistence of conductance features near $2e^2/h, 0.7(2e^2/h)$, and $0.5(2e^2/h)$. These observations indicate that perpendicular magnetic fields predominantly modify the orbital spectrum while leaving the strongly correlated spin sector intact. The resulting transport reflects the interplay between Coulomb interactions, exchange coupling, and Zeeman splitting, placing the system near the crossover between spin-coherent and spin-incoherent regimes.

The lead transition metal oxides ${\mathrm{PbTiO}}_3, {\mathrm{PbZrO}}_3$, and ${\mathrm{PbHfO}}_3$ are shown to be extremely similar in their overall properties, such as soft-mode behavior, phase transitions, and long-wavelength related characteristics. However, locally, they develop very different qualities because, as the ${\mathrm{BO}}_6$ mass increases (where B ≡ Ti, Zr, Hf), the anharmonicity of each compound increases significantly, leading to the formation of intrinsically localized modes (ILMS) or discrete breathers (DBS). This explains their exceptionally flat transverse acoustic modes. These nonlinear excitations are observed in birefringence measurements, where their coexistence with the phonon spectrum is demonstrated. While the soft modes, whether normalized by mass or temperature (long-wavelength optic and zone boundary acoustic modes), follow nearly identical temperature dependencies, the transverse acoustic modes exhibit a highly dispersion-free momentum dependence, characteristic of ILMS or DBS. Crucially, our findings support the earlier notion that the unusual dynamics are solely due to the ${\mathrm{BO}}_6$ polarizable unit, with the Pb subarrays acting merely as spectators. Furthermore, these results provide a unique explanation for the appearance of the transient phase below the phase transitions of ${\mathrm{PbZrO}}_3$ and ${\mathrm{PbHfO}}_3$, which appears to be intrinsic to these two compounds.

Synchrotron X-ray diffraction measurements of holmium were conducted up to 327 GPa using toroidal diamond-anvil cells, revealing a complete structural sequence of $\mathrm{hcp}\to \text{Sm-type}\to \mathrm{dhcp}\to \mathrm{dfcc}\to oF16\to oF8$. The $oF16\to oF8$ transition initiates around 257 GPa, approximately 60 GPa higher than that in dysprosium, and these two phases coexist up to the highest pressure studied. The transition proceeds sluggishly without a measurable volume discontinuity, indicating an anisotropic lattice rearrangement rather than abrupt $4f$ electron delocalization. The $oF8$ phase exhibits the highest incompressibility among the observed phases, completing the systematic evolution of the heavy lanthanides and underscoring the unified $oF16\to oF8$ sequence in $4f$ and $5f$ metals. First-principles calculations of phonon dispersion and enthalpy indicate that both $oF16$ and $oF8$ are dynamically stable at 325 GPa and remain nearly degenerate over a broad pressure range, consistent with the experimentally observed phase coexistence. Based on comparative analysis, this work also discusses potential method optimizations for high-pressure structural studies of rare-earth metals using toroidal diamond-anvil cells, including calibrant and gasket configurations that could improve data quality in future multi-megabar investigations.

Understanding how ${\mathrm{ABO}}_4$ oxysalt frameworks respond to compression is essential for constraining the lattice-dynamical mechanisms that govern pressure-induced structural transitions. However, intrinsic lattice instabilities are often obscured during static compression by broad mixed-phase regions. Here we measured longitudinal sound velocities ($V_{\mathrm{P}}$) of barite (${\mathrm{BaSO}}_4$) and celestite (${\mathrm{SrSO}}_4$) under shock compression up to ∼10 GPa, and performed first-principles stress-strain calculations for ${\mathrm{BaSO}}_4$. Our results show that the $V_{\mathrm{P}}$ of celestite varies smoothly with pressure over the investigated range, whereas barite exhibits a ∼6% decrease in $V_{\mathrm{P}}$ between ∼5.2 and ∼7.0 GPa. This anomaly is consistent with the $Pnma\to P{2}_1{2}_1{2}_1$ phase transition in ${\mathrm{BaSO}}_4$ but occurs at substantially lower pressure and within a narrower pressure interval than under static compression. First-principles calculations show that the Pnma lattice becomes unstable at shear stresses of ∼1.7–3.5 GPa, close to the estimated shock-induced deviatoric stresses, and that the instability involves cooperative tilting of ${\mathrm{SO}}_4$ tetrahedra and distortion of Ba–O polyhedra. These results suggest that high strain-rate shock loading couples transient deviatoric stresses to lattice instabilities, enabling access to the transition prior to equilibrium relaxation. The observed $V_{\mathrm{P}}$ softening provides experimental support for an underlying lattice instability associated with the transition. Our results highlight that sound-velocity measurements under shock compression can provide a sensitive probe of incipient lattice instability in ${\mathrm{ABO}}_4$ frameworks and illustrate how strain-rate-assisted shear instabilities reshape phase-transition pathways in complex oxysalts.

Spectroscopy serves as a key experimental pathway for probing many-body dynamics. Among them, high-harmonic generation (HHG) spectroscopy is particularly valued for its subcycle temporal resolution. Recent investigations have confirmed that excitonic effects in crystals can significantly enhance harmonic signal yield. The influence of excitonic effects on harmonic frequency have yet to be addressed. In this work, we theoretically demonstrate the collaboration mechanism to the frequency shift in the high-harmonic spectrum through two key excitonic effects: band gap renormalization and Rabi frequency renormalization. The observed band gap renormalization leads to an asymmetry of harmonic emission efficiency between the rising and falling edges of the driving laser pulse, with higher efficiency during the falling edge. This further results in a redshift of the harmonic spectrum. By contrast, the Rabi frequency renormalization with Pauli-blocking correction exhibits a tendency toward a blueshift via enhanced rising-edge emission, yet its synergy with band gap renormalization results in a pronounced redshift. In this work, we establish a direct link between exciton dynamics and the HHG process.

Classical nonlinear theories are highly successful in describing far-from-equilibrium dynamics in magnetism, including phenomena such as parametric resonance, ultrafast switching, and even chaos. However, at ultrashort length and time scales, where quantum correlations become significant, these models inevitably break down. While numerous methods exist to simulate quantum many-body spin systems, they are often limited to near-equilibrium conditions, capture only short-time dynamics, or obscure the intuitive connection between nonlinear behavior and its geometric origin in the $\mathfrak{su}\left(2\right)$ spin algebra. To advance nonlinear magnetism into the quantum regime, we develop a theory in which semiclassical spin correlations, rather than individual spins, serve as the fundamental dynamical variables. Defined on the bonds of a bipartite lattice, these correlations are inherently nonlocal, with dynamics following through a semiclassical mapping that preserves the original spin algebra. The resulting semiclassical theory captures nonlinear dynamics that are fundamentally nonclassical and naturally incorporates phenomenological damping at the level of correlations, requiring significantly less effort than quantum many-body approaches. As an application, we focus on Heisenberg antiferromagnets, which feature significant quantum effects. We predict nonlinear scaling of the mean frequency of quantum oscillations in the Néel state exhibit a nonlinear scaling state with the spin quantum number $S$. These oscillations have no classical analog and exhibit features reminiscent of nonlinear parametric resonance, as fully confirmed by exact diagonalization. The predicted dynamical features are embedded in the geometric structure of the semiclassical phase space of spin correlations, making their physical origin much more transparent than in full quantum methods. With this, semiclassical spin-correlation dynamics provide a foundation for exploring nonlinear quantum magnetism.

We investigate the chromium breathing-pyrochlore sulfide ${\mathrm{AgInCr}}_4{\mathrm{S}}_8$, a chromium-based thiospinel, by synchrotron x-ray and neutron powder diffraction, dc magnetization, and heat capacity. Diffraction confirms the $F\overline{4}3m$ breathing structure with alternating large and small $\mathrm{C}{\mathrm{r}}_4$ tetrahedra, a large breathing ratio ($d^{\prime }/d=1.106$ at 300 K), and substantial Ag/In intermixing on the $A$ sublattice ($\sim 16\%$). No structural transition or magnetic Bragg peaks are detected down to 1.5 K. An enlarged low-angle difference plot between the 1.5 and 20 K neutron diffraction patterns shows a weak broad diffuselike enhancement, consistent with short-range or frozen correlated moments within the sensitivity of the present data. Susceptibility yields a positive Weiss temperature ${\theta }_{\mathrm{W}}=+92\mathrm{K}$ and a moment enhancement in 30–60 K, while the magnetic entropy released by $\sim 30\mathrm{K}$ approaches a scale of order $R$ ln 13, together consistent with the development of short-range tetrahedral ferromagnetic correlations and an effective $S=6$ cluster-moment picture. A broad susceptibility cusp with ZFC–FC bifurcation and a low-temperature specific-heat anomaly near 9 K indicate a phenomenological glassy-freezing anomaly without long-range order. ${\mathrm{AgInCr}}_4{\mathrm{S}}_8$ provides a benchmark for the interplay of strong breathing distortion and quenched $A$-site disorder in chromium breathing pyrochlores.

Unconventional antiferromagnets with intrinsic spin splitting enable spin-polarized transport similar to ferromagnets with zero net magnetization, offering substantial potential applications in high-density, nonvolatile spintronic devices. However, achieving efficient electric-field controlled tunneling magnetoresistance (TMR) still remains a fundamental challenge. Here, we propose a general strategy based on symmetry design—constructing mirror-time reversal (${\widehat{M}}_z\widehat{T}$) symmetry—to effectively regulate antiferromagnetic TMR. Using bilayer $\mathrm{Mn}{\mathrm{Sb}}_2{\mathrm{Se}}_4$ as a model system, we demonstrate that van der Waals stacking breaks combined inversion and time reversal symmetry ($\widehat{P}\widehat{T}$), driving a transition from a spin-degenerate state to a spin-splitting unconventional antiferromagnetic phase with zero net magnetic moment. This system hosts two stable states with opposite interlayer electric polarizations, linked by ${\widehat{M}}_z\widehat{T}$ symmetry, which allows an external electric field to reversibly switch the spin-texture alignment. Accordingly, we construct an antiferromagnetic tunnel junction that achieves reversible resistance switching via polarization reversal without altering magnetic order, yielding a nonvolatile TMR ratio up to 300%. All these findings establish feasible pathways towards low-power, high-density antiferromagnetic spintronic devices.

We study the Josephson effects in the spin-triplet superconductor/altermagnet/spin-triplet superconductor junctions using the Green's function method. It is found that the current-phase difference relationships in the junctions strongly depend on the direction of the $\mathbf{d}$-vectors in the spin-triplet superconductors and the orientation angle of the altermagnet. For the given orientation angle, the 0-$\pi$ transition can be obtained when the $\mathbf{d}$-vector is rotated. The variations of the critical current of the junctions with the direction of the $\mathbf{d}$-vector, the orientation angle and the strength of altermagnetism are systematically investigated. These Josephson effects can provide the distinguishable information about the direction of the $\mathbf{d}$-vector. Compared to the existing research, the proposed altermagnetic Josephson junctions can effectively avoid the negative influence of the magnetic field on the $\mathbf{d}$-vector and can serve as a feasible scheme for the detection of the intrinsic $\mathbf{d}$-vector. The obtained 0-$\pi$ transition in the junctions can also have potential applications in the design of quantum devices.

The strength of aluminum alloys, the most widely used lightweight structural materials, mainly originates from coherent complex-structured nanoplates. Yet, the atomic-scale mechanisms governing their formation remain elusive, owing to the inherent difficulty of probing and simulating solid-state nucleation and growth events. By combining density functional theory (DFT) calculations and machine learning molecular dynamics (ML-MD) simulations, we reveal a unified “interlayer-sliding+shuffling” mechanism for three technologically significant complex-structured nanoplates—${\mathrm{T}}_1$, Ω, and ${\eta }^{\prime }/{\eta }_2$—in commercial Al alloys. Despite their distinct crystal structures, all three form via the same sequence: partial dislocations first drive the interlayer sliding to create a local hexagonal close-packed (hcp) environment, after which an unstable solute cluster, termed the basic structural transformation unit (BSTU), triggers atomic shuffling into the final complex phase. Identifying distinct BSTUs for each nanoplate enables reconstruction of their structural evolution pathways, reproducing experimental thickness distributions and enabling critical-nucleus assessment. Furthermore, we show that solute-enriched GP zones reduce stacking-fault energy and stabilize partial dislocations, while diffusional glide driven by local solute fluctuations controls their migration. These findings offer a unified physical picture of complex nanoprecipitation in aluminum alloys and may provide a useful framework for understanding $\mathrm{fcc}\to \mathrm{complex}$ transformations in related metallic systems.

In light of recent progress in the study of amorphous topological phases, we investigate the effects of structural disorder on the topological properties of a two-dimensional quantum spin Hall insulator modeled by the Bernevig-Hughes-Zhang Hamiltonian. Using a real-space formulation of the ${\mathbb{Z}}_2$ invariant for a Dirac-type Hamiltonian, we map out the phase diagram as a function of disorder strength and the mass parameter. Our results reveal that, under the influence of structural disorder, a system can either undergo a phase transition from a topologically nontrivial to a topologically trivial ($\mathrm{N}\to \mathrm{T}$) phase or from a trivial to nontrivial phase ($\mathrm{T}\to \mathrm{N}$). Remarkably, in certain parameter regimes, the system exhibits a re-entrant behavior: A topologically nontrivial phase in the perfect lattice undergoes a transition to a trivial state under the influence of weak disorder but re-emerges as the disorder strength is further increased ($\mathrm{N}\to \mathrm{T}\to \mathrm{N}$). We corroborate these findings through analysis of the bulk-boundary correspondence and transport calculations.

Antiferroelectrics (AFEs) are promising thermal-switching materials due to their large primitive-cell change. Using first-principles calculations combined with the temperature-dependent effective potential method and the Wigner transport equation, in this work, we systematically study lattice thermal conductivity (${\kappa }_L$) switching in $\mathrm{NaNb}{\mathrm{O}}_3$ across its ferroelectric (FE, $R3c$), AFE ($Pca{2}_1$), and paraelectric (PE, $Pm\text{−}3m$) phases. Results reveal sharp discontinuities in ${\kappa }_L$ at phase transitions, with a maximum switching ratio of 2.8 during the AFE–PE transition, governed primarily by particlelike conductivity (${\kappa }_p$) via abrupt phonon lifetime changes. Interestingly, in the $Pca{2}_1$ phase, wavelike conductivity (${\kappa }_c$) contributes up to 60% of ${\kappa }_L$, far exceeding its share (<25%) in other phases. The underlying mechanism is the strong coherent coupling among high-frequency near-degenerate phonon pairs. Meanwhile, the low symmetry of the $Pca{2}_1$ phase suppresses phonon lifetimes, reducing ${\kappa }_p$. These findings highlight the roles of ${\kappa }_p$ in phase-transition engineering of $\mathrm{NaNb}{\mathrm{O}}_3$ and ${\kappa }_c$ in strongly anharmonic systems, offering theoretical guidance for designing high-performance thermal switches via phase engineering.

The theory of open quantum systems is one of the most essential tools for the development of quantum technologies. A particular area of interest is in the optical response of solid state systems, where dissipation is introduced phenomenologically through the relaxation time approximation and its effects are usually gauged perturbatively. Analytical exact results for driven systems under this approximation are scarce and typically pertain only to the stationary regime. Here, we obtain the analytical solution for the current response of general single band tight-binding system driven by a uniform electric field with generic time dependence under the relaxation time approximation. We explore the effects of dissipation in two limiting cases: a monochromatic field, where we analytically deduce the effect of dissipation on high harmonic generation, and a constant electric field, where a generalization for the Esaki-Tsu equation is presented for any single band tight-binding system. We specify the results for a simple two-dimensional nearest-neighbor tight-binding lattice to emphasize the effect of the scale competition introduced by the two different neighbors in both the monochromatic and constant field cases. Finally, we compare our exact result for the constant field to the one obtained from the usual perturbation theory calculation to probe the validity of the latter.

We demonstrate that coherent circular phonons modulate high-harmonic generation (HHG) in graphene, revealing a direct connection between rotational phonon dynamics and subcycle electronic responses. While monolayer graphene yields only odd-order harmonics due to inversion symmetry, the excitation of circular phonons induces elliptically polarized sidebands, spectrally offset by the phonon frequency. These sidebands encode both the phonon energy and the relative phase between degenerate in-plane phonon modes, whose coherent superposition gives rise to rotational lattice motion. Time-domain analysis of the HHG signal enables precise extraction of this phase. Leveraging chiral probe pulses further reveals the handedness of the phonons, with distinct sideband polarization features emerging from the symmetry interplay between the phonon mode and the probe field. These findings establish HHG as a powerful spectroscopic probe for exploring phase, handedness, and dynamical symmetries of coherently excited circular phonon modes, offering an approach to understanding temporally evolving quantum materials with subcycle temporal resolution.