In the zoo of emergent symmetries in quantum many-body physics, the previously unrealized emergent spacetime supersymmetry (SUSY) is particularly intriguing. Although it was known that spacetime SUSY could emerge at the $(1+1)\mathrm{d}$ tricritical Ising transition, an experimental realization is still absent. In this Letter, we propose to realize emergent spacetime SUSY using reconfigurable Rydberg atom arrays featuring two distinct sets of Rydberg excitations, tailored for implementation on dual-species platforms. In such systems, the spacetime SUSY manifests itself in the respective correlation functions of a bosonic mode and its fermionic partner. However, the correlation function of the fermionic mode inevitably involves a string operator, making direct measurement challenging in the conventional setting. Here, we leverage the hybrid analog-digital nature of the Rydberg atom arrays, which allows for the simulation of a physical Hamiltonian and the execution of a digital quantum circuit on the same platform. This hybrid protocol offers a new perspective for uncovering the hidden structure of emergent spacetime SUSY.

Linear optical diffraction of light is a basic natural phenomenon subject to a long history study and it obeys the well-known reciprocity in transport. In this work we report observation of synergistic nonreciprocal linear and nonlinear diffraction of a Ti:sapphire femtosecond laser beam against a periodic poled lithium niobate (PPLN) thin plate nonlinear grating with a front surface corrugated with a shallow grating of a depth only 67 nm and a smooth back surface. A high peak power pump laser beam shining upon the geometrically asymmetric nonlinear grating from either the front surface and back surface will both cause significant second-order nonlinear (2nd-NL) Raman-Nath diffraction and Cerenkov radiation, in addition to apparent linear optical diffraction and modest third-order nonlinear (3rd-NL) spectral broadening. These linear, 2nd-NL, and 3rd-NL optical processes all exhibit significant differences between the front-back forward and back-front backward transport processes, in that the linear and 2nd -NL nonlinear diffraction have distinctly different patterns, while the 3rd-NL spectral broadening extent is different. The apparent synergistic nonreciprocal linear and nonlinear diffraction can be ascribed to the different coupling strength between the linear, 2nd -NL, and 3rd-NL processes of pump laser within the PPLN nonlinear grating in the forward and backward pump. The observation of both strong nonreciprocal linear and nonlinear optical diffraction would enrich the concept and physics of fundamental optical reciprocity and nonreciprocity laws.

Polymorphs commonly exist for various materials, enabling phase engineering for diverse material properties. While the crystal structures of different polymorphs can, in principle, be experimentally characterized, interpreting and understanding complex crystal structures can be very challenging. Using ${\mathrm{Ga}}_2{\mathrm{O}}_3$ as a prototype, here we show that the crystal structure of $\gamma \text{−}{\mathrm{Ga}}_2{\mathrm{O}}_3$ has long been misinterpreted from either theory or experiment. By lattice mapping based crystallographic analysis and combinatorial crystal structure search, we reveal the nature of $\gamma \text{−}{\mathrm{Ga}}_2{\mathrm{O}}_3$ as a disordered form of $\beta \text{−}{\mathrm{Ga}}_2{\mathrm{O}}_3$, which is further confirmed by Monte Carlo simulations of the order-disorder transition. Our insights are critical for correct interpretation and characterization of $\gamma \text{−}{\mathrm{Ga}}_2{\mathrm{O}}_3$, and the established physics is expected to be widely applicable to a variety of polymorphic systems.

The Kitaev honeycomb model supports gapless and gapped quantum spin liquid phases. Its exact solvability relies on extensively many locally conserved quantities. Any real-world manifestation of these phases would include imperfections in the form of disorder and interactions that break integrability. We show that the latter qualitatively alters the properties of vacancies in the gapless Kitaev spin liquid: (i) Isolated vacancies carry a magnetic moment, which is absent in the exactly solvable case. (ii) Pairs of vacancies on even or opposite sublattices gap each other with distinct power laws that reveal the presence of emergent gauge flux.

In this Letter, we propose a mechanism of an emergent quasilocalized phase in chiral symmetry classes, where the wave function along a spatial direction with weak topology is delocalized but exponentially localized along the other directions. The Anderson transition in two-dimensional chiral symmetry classes is induced by the proliferation of vortex-antivortex pairs of a U(1) phase degree of freedom, while the weak topology endows the pair with a Berry phase. We argue that the Berry phase induces spatial polarizations of the pairs along the topological direction through the quantum interference effect, and the proliferation of the polarized vortex pairs results in the quasilocalized phase.

In this study, we construct Fabry-Perot cavities in which nanostructured, thin resonant metasurfaces act as mirrors. We develop a temporal coupled-mode theory and provide an accurate description of the resonances supported by these cavities, deriving analytically their transmission characteristics. The presence of metasurface mirrors introduces a substantial group delay, causing the field concentration to shift from the bulk of the cavity towards the regions close to the two metasurfaces. This shift is accompanied by a significant increase in the quality factor of the resonances that is associated with the emergence of singular points in frequency space. These singular points exist even when the cavity separations are smaller than the cavity length of the fundamental mode in standard cavities, enabling meta-mirror Fabry-Perot cavities to outperform traditional cavities by achieving much higher quality factors despite displaying shorter cavity lengths.

Axions are hypothesized particles believed to potentially resolve two major puzzles in modern physics: the strong $CP$ problem and the nature of dark matter. Cavity-based axion haloscopes represent the most sensitive tools for probing their theoretically favored couplings to photons in the microelectronvolt range. However, as the search mass (or frequency) increases, the detection efficiency decreases, largely due to a decrease in cavity volume. Despite the potential of higher-order resonant modes to preserve experimental volume, their practical application in searches has been limited by the challenge of maintaining a high form factor over a reasonably wide search bandwidth. We introduce an innovative tuning method that uses the unique properties of auxetic materials, designed to effectively tune higher modes. This approach was applied to the ${\mathrm{TM}}_{020}$ mode for a dark matter axion search exploring a mass range from 21.38 to $21.79\mathrm{\mu }\mathrm{eV}$, resulting in the establishment of new exclusion limits for axion-photon coupling greater than approximately ${10}^{-13}{\mathrm{GeV}}^{-1}$. These findings should allow use of higher-order modes for cavity haloscope searches.

Emerging applications of metasurfaces in classical and quantum optics are driving the need for precise polarization control of nearly-degenerate, high quality ($Q$)-factor modes. However, current approaches to creating specifically polarized pairs of modes force a trade-off between maintaining high $Q$ factors and robustness. Here, we solve this challenge by employing pairwise generation, annihilation, and positioning of polarization singularities, derived from symmetry-guaranteed pairs of symmetry-protected bound states in the continuum. We experimentally demonstrate this design paradigm in silicon metasurfaces with mode splittings of $\approx 20\mathrm{nm}$, mode splitting deviations as low as 1 nm, and $Q$ factors up to 200. This approach opens new avenues for enhancing metasurface performance across a diverse range of applications, including sensing, modulating, nonlinear mixing, and generating quantum light.

Noncentrosymmetric two-dimensional superconductors with large spin-orbit coupling offer an opportunity to explore superconducting behaviors far beyond the Pauli limit. One such superconductor, few-layer $T_d\text{−}{\mathrm{MoTe}}_2$, has large upper critical fields that can exceed the Pauli limit by up to 600%. However, the mechanisms governing this enhancement are still under debate, with theory pointing toward either spin-orbit parity coupling or tilted Ising spin-orbit coupling. Moreover, ferroelectricity concomitant with superconductivity has been recently observed in the bilayer, where strong changes to superconductivity can be observed throughout the ferroelectric transition pathway. Here, we report the superconducting behavior of bilayer $T_d\text{−}{\mathrm{MoTe}}_2$ under an in-plane magnetic field, while systematically varying magnetic field angle and out-of-plane electric field strength. We find that superconductivity in bilayer ${\mathrm{MoTe}}_2$ exhibits a twofold symmetry with an upper critical field maxima occurring along the $b$ axis and minima along the $a$ axis. The twofold rotational symmetry remains robust throughout the entire superconducting region and ferroelectric hysteresis loop. Our experimental observations of the spin-orbit coupling strength (up to 16.4 meV) agree with the spin texture and spin splitting from first-principles calculations, indicating that tilted Ising spin-orbit coupling is the dominant underlying mechanism.

We propose a variational wave function to represent quantum skyrmions as bosonic operators. The operator faithfully reproduces two fundamental features of quantum skyrmions: their classical magnetic order and a “quantum cloud” of local spin-flip excitations. Using exact numerical simulations of the ground states of a 2D chiral magnetic model, we find two regions in the single-skyrmion state diagram distinguished by their leading quantum corrections. We use matrix product state simulations of the adiabatic braiding of two skyrmions to verify that the operator representation of skyrmions is valid at large interskyrmion distances. Our work demonstrates that skyrmions can be approximately coarse-grained and represented by bosonic quasiparticles, which paves the way toward a field theory of many-skyrmion quantum phases and, unlike other approaches, incorporates the microscopic quantum fluctuations of individual skyrmions.

Bilayer materials may support interlayer excitons comprised of electrons in one layer and holes in the other. In experiments, a nonzero exciton density is typically sustained by a bias chemical potential, implemented either by optical pumping or by electrical contacts connected to the two layers. We show that if charge can tunnel between the layers, the chemical potential bias means that an exciton condensate is in the dynamical regime of ac Josephson effect. It has physical consequences such as tunneling currents and the ability to tune a condensate from bright (emitting coherent photons) to dark by experimental controlling knobs. If the system is placed in an optical cavity, coupling with cavity photons favors different dynamical states depending on the bias, realizing superradiant phases.

Filamentous-actin ($F$-actin) crosslinking within the cell cytoskeleton mediates the transmission of mechanical forces, enabling changes in cell shape, as occurs during cell division and cell migration. Crosslinking by actin binding proteins (ABPs) generally increases the connectivity of the $F$-actin network, but also increases network rigidity. As a result, there is a narrow range in the concentration of crosslinker protein at which $F$-actin networks are both connected and labile. Another ABP, cofilin, severs $F$-actin filaments at high $p\mathrm{H}$ through increasing their bending flexibility and concentrating mechanical stress, inducing fragmentation. By contrast, at lower $p\mathrm{H}$, cofilin increases filament flexibility yet does not sever. Instead, it forms disulfide bonds, which crosslink $F$-actin into bundles, and bundles into networks. Here, we combine light microscopy and rheology to determine the impact of two potentially opposing effects on the mechanics of $F$-actin networks—increased flexibility at the filament level, and increased connectivity at the network level. Indeed, by linear rheology, we find that these mechanisms are counterbalanced, such that cofilactin network moduli are only weakly dependent on cofilin concentration over a broad range, in contrast to the dramatic stiffening that occurs with $F$-actin crosslinking protein. Further, by nonlinear rheology, the network stiffens at a higher stress than crosslinking protein, indicative of a broader range in which the material remains flexible. These results may enable $F$-actin networks to increase connectivity without heavy penalties to rigidity, and thus provide a new route to modulating active polymer mechanics unseen using traditional $F$-actin accessory proteins.

Long-range spin-spin interactions are known to generate nonequilibrium dynamics that can squeeze the collective spin of a quantum spin ensemble in a scalable manner, leading to states whose metrologically useful entanglement grows with system size. Here, we show theoretically that scalable squeezing can be produced in 2D U(1)-symmetric systems even by short-range interactions, i.e., interactions that at equilibrium do not lead to long-range order at finite temperatures, but rather to an extended Berezinskii-Kosterlitz-Thouless critical phase. If the initial state is a coherent spin state in the easy plane of interactions, whose energy corresponds to a thermal state in the critical Berezinskii-Kosterlitz-Thouless phase, the nonequilibrium dynamics exhibits critical slowing down, corresponding to a power-law decay of the collective magnetization in time. This slow decay protects scalable squeezing, whose scaling reveals in turn the decay exponent of the magnetization. Our results open the path to realizing massive entangled states of potential metrological interest in many relevant platforms of quantum simulation and information processing—such as Mott insulators of ultracold atoms, or superconducting circuits—characterized by short-range interactions in planar geometries.

Semi-inclusive hadron production in longitudinally polarized deep-inelastic lepton-nucleon scattering is a powerful tool for resolving the quark flavor decomposition of the proton’s spin structure. We present the full next-to-next-to-leading order QCD corrections to the coefficient functions of polarized semi-inclusive deep-inelastic scattering (SIDIS) in analytical form, enabling the use of SIDIS measurements in precision studies of the proton spin structure. The numerical impact of these corrections is illustrated by a comparison with data of polarized single-inclusive hadron spectra from the DESY HERMES and CERN COMPASS experiments.

Polarized semi-inclusive deep-inelastic scattering (SIDIS) is a key process in the quest for a resolution of the proton spin puzzle. We present the complete results for the polarized SIDIS process at next-to-next-to-leading order (NNLO) in perturbative quantum chromodynamics. Our analytical results include all partonic channels for the scattering of polarized leptons off hadrons and a spin-averaged hadron identified in the final state. A numerical analysis of the NNLO corrections illustrates their significance and the reduced residual scale dependence in the kinematic range probed by the future electron-ion collider.