Field-free deterministic switching of magnetization by electric current is at the heart of spin-orbit-torque devices. It is widely believed that structural inversion symmetry breaking is an indispensable prerequisite for such switching. Here we propose that by exploiting the nonlinear response regime, a time-reversal-odd spin polarization offers a robust dynamical route to entirely circumvent this symmetry requirement. Using a macrospin model, we map out the dynamic phase diagram of the magnetization driven by this nonlinear spin polarization and identify the conditions required for deterministic switching. As a concrete example, we demonstrate field-free magnetization switching via numerical simulations of a centrosymmetric, two-band magnetic Weyl semimetal model.

We investigate the superconducting properties of ${\mathrm{RuO}}_2$ films grown on ${\mathrm{TiO}}_2$ substrates by combining film fabrication and transport measurement with $\mathrm{ab\; initio}$ calculation. Experimentally, we grow several ${\mathrm{RuO}}_2$ (110) thin films on ${\mathrm{TiO}}_2$ (110) substrates and observe superconductivity with critical temperature ($T_c$) of ∼2.0 K in 20-nm and 30-nm ${\mathrm{RuO}}_2$ (110) thin films. Theoretically, we study the superconductivity in both ${\mathrm{RuO}}_2$ (110) and ${\mathrm{RuO}}_2$ (100) epitaxial films within McMillan formalism of isotropic Migdal-Eliashberg theory, using the normal state properties from $\mathrm{ab\; initio}$ calculations. The crystal structures of the films are obtained with the out-of-plane lattice constant and atomic positions determined by ab initio calculations while the in-plane lattice constants held fixed to the experimental values. Among the salient results, the calculated phonon dispersion relations of all the considered ${\mathrm{RuO}}_2$ films have no imaginary frequencies, i.e., the epitaxial films are dynamically stable. Importantly, our ab initio calculations reveal that, independent of the film orientation, the [001] compressive strain ${\epsilon }_{\left[001\right]}$ pushes the flat Ru $d_{z^2}$-dominant bands towards the Fermi level $\left(E_F\right)$ and significantly soften the out-of-plane acoustic phonon mode near the R point in the Brillouin zone, which substantially enhances the electron-phonon coupling (EPC) strength $\lambda$ and hence the calculated $T_c$ in the ${\mathrm{RuO}}_2$ films. Remarkably, the amount of the phonon softening and the enhanced $T_c$ increase almost linearly with the increasing ${\epsilon }_{\left[001\right]}$. The calculated $T_c$ for the films with thickness $t\ge 20\mathrm{nm}$ agree well with the experimental $T_c$. For example, the theoretical $T_c$ of 2.8 K for 20-nm ${\mathrm{RuO}}_2$ (110) film and 0.8 K for 28-nm ${\mathrm{RuO}}_2$ (100) film are close to the experimental $T_c$ of 2.0 K and 1.0 K, respectively. These findings demonstrate that, among other things, lattice mismatch strain provides an effective route for tuning phonon-mediated superconductivity in ${\mathrm{RuO}}_2$ and other thin films.

Recently, the superconducting diode effect, characterized by unequal critical currents in opposite directions, has been observed experimentally and predicted theoretically in models of bulk superconductors and Josephson junctions. In this work, we construct a Josephson junction using a recently discovered unconventional coplanar magnet, the $p$-wave magnet, with proximity-induced superconductivity, and demonstrate the emergence of a field-free Josephson diode effect (JDE). The barrier region is formed by another unconventional collinear magnet, namely, an altermagnet. We show that in addition to time-reversal and inversion symmetries, breaking the mirror symmetry $M_{yz}$ is essential for the JDE in our geometry, and that the unconventional-magnet heterostructure provides a platform to isolate this symmetry requirement. Unlike earlier models that realize JDE using unconventional magnets, this setup does not require Rashba spin-orbit coupling or different superconductors across the junction. Instead, $p$-wave magnet provides inversion-asymmetric spin splitting while the altermagnetic barrier breaks mirror symmetry, together giving rise to the diode response. Finally, we establish the robustness of the JDE against interface mismatch, disorder, finite-temperature effects, and variations in the induced superconducting gap over a broad parameter regime, making the proposed heterostructure a promising platform for field-free superconducting diodes.

We theoretically investigate circular dichroism (CD) in second- and third-harmonic generation (SHG and THG) in the chiral topological semimetal CoSi. We demonstrate that both SHG and THG exhibit dichroic responses of order unity, while their robustness against spectral broadening is strikingly different. Specifically, while SHG-CD is strongly suppressed by dissipation, THG-CD remains robust over a wide frequency range. We show that this qualitative difference originates from the phase structure of the nonlinear current, where SHG-CD arises from subleading interference processes that are sensitive to dephasing, whereas THG-CD emerges already at the leading nonlinear order and is, therefore, protected against spectral broadening. As a result, THG-CD provides a robust probe of chirality encoded in nonequilibrium electronic dynamics. We further reveal nonmonotonic frequency dependences and pronounced sensitivity of harmonic emission to the polarization state and crystallographic orientation of the driving field. Our results provide a representative example of robust nonlinear chiroptical responses in chiral topological semimetals and highlight the potential of high-harmonic spectroscopy as a probe of phase-resolved electronic dynamics.

A vital goal in spintronics is the efficient electrical generation of spin currents, a pursuit that has recently focused on using antiferromagnets (AFMs) as spin current sources. It has been demonstrated that antiferromagnets with broken $PT$ symmetry (parity + time reversal) can efficiently generate longitudinal and transverse spin currents. At the same time, it has been generally thought that antiferromagnets with $PT$ symmetry ($PT$-AFMs) forbid the longitudinal spin polarization due to their spin-degenerate band structure. Here, in contrast with this common expectation, we show, using theoretical analysis based on magnetic point-group symmetry, that most $PT$-AFMs can generate longitudinal spin currents due to spin-orbit coupling. Using density-functional theory, we calculate the longitudinal spin conductivity of representative $PT$-AFMs, $L{1}_0$-MnPt and $\mathrm{M}{\mathrm{n}}_2\mathrm{Au}$ and show that its magnitude is comparable to that of their $PT$-broken counterparts. Our symmetry-enabled classification of antiferromagnets and theoretical results for the longitudinal spin conductivity in representative $PT$-AFMs expand our understanding of spin transport and show the possibility of robust spin-current generation in a broad range of spin-degenerate antiferromagnets.

As a new and promising family of two-dimensional (2D) materials, MBenes have attracted attention owing to their excellent stability, high electrical conductivity, and versatile physicochemical properties. However, studies on the intrinsic physical properties of MBenes, including the superconductivity and band topology, are still relatively limited. In this study, we propose an effective strategy to regulate the superconducting and topological properties of ${\mathrm{Mo}}_2\mathrm{B}$ by combining surface functionalization and layer-number modulation based on first-principles calculations. Starting from pristine ${\mathrm{Mo}}_2\mathrm{B}$ in both the $1T$ and $2H$ phases, we investigate hydrogenated (${\mathrm{Mo}}_2{\mathrm{BH}}_2$), oxidized (${\mathrm{Mo}}_2{\mathrm{BO}}_2$), and quintuple-layer (${\mathrm{Mo}}_2{\mathrm{B}}_3$) derivatives. Thirteen thermodynamically and dynamically stable structures are identified. Among them, $H_1\text{−}{\mathrm{Mo}}_2{\mathrm{BO}}_2$ and $T_2\text{−}{\mathrm{Mo}}_2{\mathrm{B}}_3$ exhibit strong electron-phonon coupling and high superconducting transition temperatures of 32 and 28 K, respectively. Notably, $T_2\text{−}{\mathrm{Mo}}_2{\mathrm{B}}_3$ also shows nontrivial band topology characterized by a $Z_2$ index of 1 and topological edge states. Our findings uncover rich properties in ${\mathrm{Mo}}_2\mathrm{B}$-based MBenes and provide valuable insights for designing novel 2D materials with coexisting superconducting and topological states.

Methylammonium lead iodide perovskite, ${\mathrm{CH}}_3{\mathrm{NH}}_3{\mathrm{PbI}}_3$ (${\mathrm{MAPbI}}_3$), has attracted tremendous interest for its exceptional optoelectronic performance. However, the effect of MA arrangement on charge carrier recombination remains unclear. Here, ${\mathrm{BF}}_4$ doping is introduced to preserve distinguishable ferroelectric (FE) and antiferroelectric (AFE) MA configurations over the accessible simulation timescale, enabling a direct comparison of the influence of MA arrangement on carrier recombination. Using time-domain density functional theory and ab initio nonadiabatic molecular dynamics, we demonstrate that the nonradiative recombination in ${\mathrm{BF}}_4$-doped ${\mathrm{MAPbI}}_3$ perovskite with an AFE MA arrangement (${\mathrm{BF}}_4$-AFE) is slowed by an order of magnitude when compared with that in the FE structure. The strong spatial variation of the built-in electric field in the AFE structure introduces effective charge separation. The strong electrostatic repulsion between adjacent MA molecules in the ${\mathrm{BF}}_4$-AFE structure weakens MA-related atomic fluctuations, which strongly suppresses the high-frequency electron–vibration interaction. These effects result in a short pure dephasing time and a weak nonadiabatic coupling in the ${\mathrm{BF}}_4$-AFE structure, finally revealing its long carrier lifetime. This work provides mechanistic insight into how MA molecular arrangement influences carrier recombination in ${\mathrm{MAPbI}}_3$.

Edge states in lattices typically rely on defects, topology, or parameter tuning, and occupy narrow spectral windows. Here, we demonstrate an edge-dominated mechanism driven by the Poincaré conformal metric. By projecting the hyperbolic metric onto elastic trusses, we show that the spatially varying bar lengths naturally embed the metric into the structural dynamic properties. This spatial modulation of the local dynamic scale inherently drives higher-index eigenmodes toward the boundary, yielding an accumulation of edge states. Furthermore, conformal mapping extends this mechanism to arbitrary boundaries, enabling the design of interconnected boundary-channel networks. Transient wave propagation confirms boundary-guided transport, establishing a topology-free route for programmable wave localization and energy focusing in mechanical metamaterials.

By precisely controlling the loss rate and the coupling strength in an open magnonic cavity, the first experimental demonstration in general pseudo-Hermitian systems of two different singularities with nonreciprocity and selectivity has been achieved. One of the singularities is the exceptional point (EP), for which we have innovatively proposed and experimentally realized the case of a nonreciprocal single EP. The experimental phenomenon of coherent and dissipative couplings occurs simultaneously in the case of a nonreciprocal single EP. The theoretical results show distinct mode switching and topological properties for different directions by encircling an EP. Another singularity is the bound state in the continuum (BIC), where we have achieved a nonreciprocal BIC dominated by the dissipative coupling. Our results demonstrate that the planar cavity with both the standing and traveling waves can be an ideal magnonic polariton platform to study pseudo-Hermitian physics.

We report the realization of a metallic flat band in the marcasite compound ${\mathrm{MnSb}}_2$. The material was synthesized under high pressure, and its crystal structure was established by x-ray diffraction. Electrical and thermoelectric transport measurements reveal signatures of a flat band near the Fermi level that persist across three structural, magnetic, and electronic transitions. These observations are supported by extensive density-functional-theory calculations. Related marcasite diantimonides, including ${\mathrm{FeSb}}_2$ and ${\mathrm{CrSb}}_2$, also host flat bands, but these lie far from the Fermi level and therefore do not produce a metallic flat-band state. ${\mathrm{MnSb}}_2$ therefore emerges as the only known metallic marcasite antimonide in which a flat band lies in the vicinity of the Fermi level.

We construct effective $\mathrm{U}\left(2\right)$ Chern-Simons-Ginzburg-Landau theories for Abelian and non-Abelian fractional quantum Hall hierarchies that had previously been described only through categorical data or trial wave functions. Our framework captures both Abelian hierarchy states built on half-filled Pfaffian-type parents and non-Abelian hierarchies emerging from Abelian states. It reproduces all filling fractions obtained from wave-function and categorical constructions and, moreover, uniquely determines the corresponding topological orders. We also identify an intriguing particle-hole symmetry relating two hierarchy sequences, one built on a trivial insulator and the other on the $\nu =1$ integer quantum Hall state, which respectively generate the Read-Rezayi sequences and their particle-hole conjugates under the same hierarchy construction.

The Hubbard model at finite chemical potential is a cornerstone for understanding doped correlated systems, but simulations are severely limited by the sign problem. In the auxiliary-field formulation, the spin basis mitigates the sign problem, yet severe ergodicity issues have limited its use. We extend recent advances with normalizing flows at half filling to finite chemical potential by introducing an annealing scheme enabling ergodic sampling. Compared to state-of-the-art hybrid Monte Carlo in the charge basis, our approach accurately reproduces exact diagonalization results while reducing statistical uncertainties by an order of magnitude, opening another path for simulations of doped correlated systems.

A single-crystal compensated ferrimagnet ${\mathrm{Ni}}_4{\mathrm{Nb}}_2{\mathrm{O}}_9$, consisting of two antiferromagnetically coupled ferromagnetic (FM) $\mathrm{N}{\mathrm{i}}^{2+}$ layers with opposite moments in the ab plane, exhibiting noninterface exchange bias (EB), was investigated. The magnetization hysteresis loops $M\left(\theta \right)$, measured at a weak field H rotating in FM layers clockwise and then counterclockwise, show two successive M flips in opposite directions with a large hysteresis of the flip angle ${\theta }_{\mathrm{MR}}$. It was found that the angle ${\theta }_{\mathrm{MR}}$ shifts due to EB to higher or lower values, depending on the sign of the unidirectional anisotropy EB specified by the field cooling protocol. Furthermore, the EB effect also influences the temperature of spontaneous switching $T_{\mathrm{sw}}$ from negative to positive magnetization, which occurs below $T_{\mathrm{comp}}=33\mathrm{K}$, at a constant field H. Namely, $T_{\mathrm{sw}}$ decreases in the presence of positive unidirectional anisotropy and increases in the presence of negative anisotropy, indicating that the energy required to flip M depends on the sign of EB. The features discovered allow us to more fully comprehend the nature of the EB effect in coupled FM layers of compensated ${\mathrm{Ni}}_4{\mathrm{Nb}}_2{\mathrm{O}}_9$ ferrimagnet.

Rare-earth-ion-doped crystals have emerged as a promising platform for quantum technologies, owing to their narrow telecom-band optical emission, long spin memory, and compatibility with silicon integrated photonic architectures. However, the realization of scalable quantum devices requires host materials with intrinsically dilute spin environments to suppress decoherence. In this context, erbium $\left({\mathrm{Er}}^{3+}\right)$ doped cerium oxide $\left({\mathrm{CeO}}_2\right)$ is an attractive candidate due to the ultralow concentration of nuclear spins in the host matrix and its compatibility with silicon-based technologies. Here we perform a comprehensive investigation of the coherence properties of an ${\mathrm{Er}}^{3+}$ electron spin qubit in ${\mathrm{CeO}}_2$ via semiclassical as well as detailed cluster correlation expansion simulations. By systematically exploring magnetic field strength, pulse sequences, erbium concentration, and spin temperature, we identify regimes where decoherence from the spin bath is strongly suppressed. Our investigations illustrate that at dilute doping concentration (of the order of 10 ppb) and sub-Kelvin temperatures, operation near clock transitions enables Hahn-echo coherence times to approach the second timescale even at natural isotopic abundance. Importantly, from a practical standpoint, coherence times on the order of $\sim 10$ ms are expected even at liquid helium temperature (about 2 K) for similar concentrations. Moreover, we demonstrate that an additional enhancement can be obtained with conventional multi-$\pi$-pulse dynamical decoupling protocols. Thus, our findings establish ${\mathrm{Er}}^{3+}$ doped ${\mathrm{CeO}}_2$ as a front-runner for realizing spin qubits, quantum memories, and integrated quantum networks.

High temperature is usually expected to destroy order: as the Gibbs state approaches the infinite-temperature limit, it becomes an equal-weight ensemble over all states and the system is generically disordered. Recent works showed that entropic order can violate this expectation through coupling to bosons in classical lattice models and quantum field theories, where the ordered states have higher entropy. Here we present new analytic methods for constructing quantum lattice models that exhibit entropic orders. In particular, we construct quantum lattice models with continuous symmetry breaking at high temperature in $1+1$ dimensions and clarify how entropic order can evade the Hohenberg-Mermin-Wagner theorems. We also construct high-temperature entropic $p+ip$ chiral topological superconducting states in $2+1$ dimensions with temperature-independent anyon correlation functions. In addition, we obtain a broad family of high-temperature entropic nonchiral topological orders. We show that the entropic topological orders have strong higher-form symmetries at high temperature unlike the conventional topological orders, and the symmetry is spontaneously broken. These results follow from two general constructions that couple a given lattice model with a low-temperature ordered phase either to ordered bosons, or for local commuting-projector Hamiltonians, to more general bosonic degrees of freedom.

We study scattering in noninteracting multiterminal quantum wire junctions and show that junctions with dihedral symmetry can exhibit exact zero-reflection points for $N\ge 4$ terminals. By analyzing the scattering matrix, we identify these reflectionless points in the $(E,t^{\prime })$ parameter space, where $E$ is the incident particle energy and $t^{\prime }$ is the junction hopping amplitude. These points exhibit an even-odd dependence on $N$ and converge asymptotically to a common limiting value in the large-$N$ limit. We show that the reflectionless points are characterized by an integer winding number associated with the phase of the reflection amplitude, providing a topological description for their stability against weak on-site disorder. We also consider junctions with broken time-reversal symmetry and find that a magnetic flux can induce additional reflectionless points, including for the $N=3$ case. For a four-terminal junction threaded by a $\pi$-flux, we identify a unique parameter regime in which the reflection amplitude vanishes over the entire energy band. Finally, we discuss experimental signatures through the behavior of Friedel oscillations and examine the stability of these reflectionless points in the presence of weak interactions.

The ultrahigh thermal conductivity of diamond, relevant to the momentum-conserving phonon normal process, holds exceptional promise for advanced micro/nanoscale thermal management. However, efficient modeling of collective phonon transport in complex three-dimensional diamond structures remains challenging. Here, we develop a computational approach for phonon transport in complex diamond micro- and nanostructures by directly solving the phonon Boltzmann transport equation under Callaway's dual relaxation model with first-principles inputs. As a result, our model provides a good quantitative explanation of the thermal conductivities of diamond nanowires, nanobeams and cuboids. Furthermore, we analyze the effects of size and temperature on mode-resolved phonon hydrodynamic transport in natural and isotopically purified diamond microfilms. Finally, the computational framework is applied to porous diamond structures to reveal the effects of neck width and isotopic concentration on nondiffusive phonon transport. This work thus promotes both efficient modeling and physical insights into collective phonon transport in diamond micro- and nanostructures, offering guidance for future experimental measurements and engineering applications.

We study a minimal square-lattice model to examine the relation between momentum-space altermagnetic band geometry and real-space Ising criticality in a coupled fermion-Ising setting. In this model, itinerant fermions with explicitly spin-dependent nearest-neighbor hopping are locally coupled to transverse-field Ising moments. The hopping anisotropy parameter $\alpha$ tunes a $d_{x^2-y^2}$-type altermagnetic band geometry in momentum space, whereas the transverse field $h$ controls real-space antiferromagnetic (AFM) fluctuations and drives the finite-temperature AFM–paramagnetic (PM) transition of the Ising sector. Using determinant quantum Monte Carlo simulations, we show for the representative $\alpha <1$ case studied in detail, $\alpha =0.5$, that the momentum-space band-geometry fingerprint remains visible in the coupled system: the spin-resolved occupation imbalance $n_{\uparrow }\left(\mathbf{k}\right)-n_{\downarrow }\left(\mathbf{k}\right)$ displays a sign-changing structure that follows the underlying spin-split Fermi-surface geometry. By contrast, finite-size scaling of the staggered Ising order parameter indicates that, in the representative comparison between $\alpha =0.5$ and $1.0$, the extracted thermal critical fields remain numerically close on the scale resolved by our finite-size analysis at both $T/t=0.5$ and $0.2$. We argue that this separation reflects the coexistence of a tunable momentum-space altermagnetic band geometry with the nesting structure of the half-filled nearest-neighbor bare kinetic term, which remains an important constraint on the AFM channel in this benchmark. Our results show that, in this controlled setting, a visible altermagnetic band-geometry fingerprint in momentum space need not imply a comparably large shift of the collective real-space magnetic phase boundary.