The corner problem is a century-old canonical scattering problem describing wave diffraction at a quarter-plane spatial discontinuity. Here, we study its space-time analog: wave scattering at a corner in space-time, arising at a time-switched spatial interface. We highlight and resolve an inconsistency between spatial and temporal boundary conditions arising in this problem, and analytically demonstrate the emergence of shock waves launched by the scattering process. After numerically verifying our theory, we realize and experimentally probe the scattering at a space-time corner arising at the edge of a time-switched waveguide. Our results unveil and efficiently model the unusual phenomena arising at the spatial interface between time-modulated and static media, of great relevance for the growing field of spatiotemporal metamaterials.

We present a controlled numerical study of the Berezinskii-Kosterlitz-Thouless (BKT) transition in the one-dimensional Bose-Hubbard model at unit filling, providing evidence of the characteristic logarithmic finite-size scaling of the BKT transition. Employing density matrix renormalization group and quantum Monte Carlo simulations under periodic boundary conditions, together with a systematic finite-size scaling analysis of bipartite particle number fluctuations, we resolve boundary-induced complications that previously obscured critical scaling. We demonstrate that a suitably chosen central region under open boundaries reproduces universal renormalization group signatures, reconciling earlier discrepancies. Finally, leveraging a nonparametric Bayesian analysis, we determine the critical interaction strength with high precision to be $U_c/J=3.275(2)$, establishing a benchmark for BKT physics in one-dimensional quantum models.

The interactions between water molecules and gold surfaces are central to biocompatibility and electrocatalysis, yet their fundamental nature remains highly controversial. Recent findings indicating a molecular-level hydrophobicity have challenged the classical view of gold being hydrophilic. Using surface-specific spectroscopy and ab initio simulations, we demonstrate that gold is neither hydrophobic nor hydrophilic in the classical sense, but exhibits strong electronic interactions with water, resulting in an orientation-dependent electronic heterogeneity. These findings are important for the properties of metal-aqueous interfaces with broad applications.

Ultralow friction offers great potential for energy-efficient applications. However, the superlubric sliding of a flake is often plagued by persistent finite friction arising from incomplete moiré tiles at flake edges. To tackle this challenge, we develop a theory of structural frictionless interface based on moiré geometry. Our theory predicts the existence of a directional frictionless interface, which can further evolve to two kinds of all-direction frictionless interfaces, even when the total flake area is not a multiple of the size of a complete moiré tile. Before reaching the frictionless state, friction scales with flake area via a geometry-dependent proportionality factor that encodes frictionless directions, agreeing with large-scale molecular dynamics simulations for both homogeneous or heterogeneous interfaces. Our theory further paves the way for designing frictionless motions in double-interface nanoconfinement channels. Our work provides insights into the creation of structural frictionless interfaces for future advancements in nanoscale tribology and nanoconfinement transport.

Inspired by recent experimental findings, we investigate various scenarios of the doped Hubbard model with impurity potentials. We calculate the lattice Green’s function in a finite-size cluster and then map it to the continuum real space, which allows for a direct comparison with scanning tunneling microscopy measurements on the local density of states. Our simulations successfully reproduce experimental data, including the characteristic stripe- and ladder-shaped structures observed in cuprate systems. Moreover, our results establish a connection between previous numerical findings on stripe-ordered ground states and experimental observations, thus providing new insights into microscopic mechanisms of the Mott insulator to superconductor transition in cuprates.

Degeneracy appears ubiquitously in physical systems. Exceptional points, the non-Hermitian degeneracies, have unveiled numerous novel phenomena that have no counterparts in Hermitian degeneracies—diabolic points. Here, we observe a hybrid degenerate point (HP) in a projected non-Hermitian system, namely a subsystem obtained by projecting a metasurface characterized by a Hermitian scattering matrix. In the projected space, the metasurface is found naturally anchored at the merging point of two exceptional curves, each carrying opposite chirality. The HP exhibits a unique topology that encodes features of both Hermitian and non-Hermitian degeneracies, thereby exhibiting linear and square-root sensitivities simultaneously. We conceptually validate and experimentally confirm the projected HP using a passive and lossless acoustic metagrating, uncovering its unique singular behavior: the pronounced anisotropic sensitivity to perturbations. Our findings highlight the potential for exploring degenerate states via the projective Hilbert space and pave the way for extreme wave manipulation in open spaces.

Symmetry engineering is an effective approach for generating emergent phases and quantum phenomena. In magnetic systems, the Dzyaloshinskii-Moriya (DM) interaction is essential for stabilizing chiral spin textures. The symmetry manipulation of DM vectors, described in three dimensions, could provide a strategy toward creating abundant topologically magnetic phases. Here, we have achieved breaking the rotational and mirror symmetries of the three-dimensional DM vectors in a strongly correlated ferromagnet, which were directly measured through the nonreciprocal spin-wave propagations in both in-plane and out-of-plane magnetic field geometries. Combining cryogenic magnetic force microscopy and micromagnetic simulations, we discover a bimeron phase that emerges between the spin spiral and skyrmion phases under an applied magnetic field. Such an artificially manipulated DM interaction is shown to play a critical role in the formation and evolution of the large-area bimeron lattice, a phenomenon that could be realized across a broad range of materials. Our findings demonstrate that symmetry engineering of the DM vectors can be practically achieved through epitaxial strain, paving the way for the creation of diverse spin topologies and the exploration of their emergent functionalities.

Exploring the photoinduced dynamics of chiral states offers promising avenues for advanced control of condensed matter systems. Photoinduced or photoenhanced chirality in $1T\text{−}{\mathrm{TiSe}}_2$ has been suggested as a fascinating platform for optical manipulation of chiral states. However, the mechanisms underlying chirality training and its interplay with the charge density wave (CDW) phase remain elusive. Here, we use time-resolved x-ray diffraction (trXRD) with circularly polarized pump lasers to probe the photoinduced dynamics of chirality in $1T\text{−}{\mathrm{TiSe}}_2$. We observe a notable ($\sim 20\%$) difference in CDW intensity suppression between left and right circularly polarized pumps. Additionally, we reveal momentum-resolved circular dichroism arising from domains of different chirality, providing a direct link between CDW and chirality. An immediate increase in CDW correlation length upon laser pumping is detected, suggesting the photoinduced expansion of chiral domains. These results both advance the potential of light-driven chirality by elucidating the mechanism driving chirality manipulation in ${\mathrm{TiSe}}_2$, and they demonstrate that trXRD with circularly polarized pumps is an effective tool for chirality detection in condensed matter systems.

We experimentally demonstrate that anti-parity-time (anti-$\mathcal{P}\mathcal{T}$) symmetry can induce a negative refractive index (NRI) in a coupled photon-magnon hybrid system. Using an analytical circuit model, we show that the non-Hermitian dynamics originating from anti-$\mathcal{P}\mathcal{T}$ symmetry give rise to antiphase propagation, reversing the phase velocity and resulting in an NRI. Furthermore, we identify cooperativity as the critical threshold parameter dictating the presence of an NRI in the anti-$\mathcal{P}\mathcal{T}$-symmetric regime. These findings provide an alternative framework for manipulating wave propagation and refractive properties in non-Hermitian hybrid quantum systems, opening avenues for advanced control of wave phenomena using magnetic materials.

Recent advances in synthetic methods enable designing subunits that self-assemble into structures with precise, finite sizes and well-defined architectures, but yields are frequently suppressed by the formation of off-target metastable structures. Increasing the complexity (the number of distinct subunit types) can inhibit off-target structures, but leads to slower kinetics and higher synthesis costs. Here, we study icosahedral shells formed of programmable triangular subunits as a model system, and identify design principles that produce the highest target yield at the lowest complexity. We use a symmetry-based construction to create a range of design complexities, starting from the maximal symmetry Caspar-Klug assembly up to the fully addressable, zero-symmetry assembly. Kinetic Monte Carlo simulations reveal that the most prominent defects leading to off-target assemblies are disclinations at sites of rotational symmetry. We derive symmetry-based rules for identifying the optimal (lowest complexity, highest symmetry) design that inhibits these disclinations, leading to robust high-fidelity assembly of targets with arbitrarily large, yet precise, finite sizes. The optimal complexity varies nonmonotonically with target size, with “magic” sizes appearing for high-symmetry designs in which symmetry axes do not intersect vertices of the triangular net. The optimal designs at magic sizes require 12 times fewer inequivalent interaction types than the (minimal symmetry) fully addressable construction, which greatly reduces the timescale and experimental cost required to achieve high-fidelity assembly of large targets. This symmetry-based principle for pruning off-target assembly generalizes to diverse architectures with different topologies.

We put forward several information-theoretic measures for analyzing the uncertainty of fermionic phase-space distributions using the theory of supernumbers. In contrast to the bosonic case, the anticommuting nature of Grassmann variables allows us to provide simple expressions for the Glauber $P$, Wigner $W$, and Husimi $Q$ distributions of the arbitrary state of a single fermionic mode. It appears that all physical states are Gaussian and, thus, can be described by positive or negative thermal distributions (over Grassmann variables). We then prove several fermionic uncertainty relations, including notably the fermionic analogs of the (yet unproven) phase-space majorization and Wigner entropy conjectures for a bosonic mode, as well as the Lieb-Solovej theorem and the Wehrl-Lieb inequality. Our central point is that, although fermionic phase-space distributions are Grassmann-valued and do not have a straightforward interpretation, the corresponding uncertainty measures are expressed as Berezin integrals, which take on real values and are physically relevant.

We demonstrate the existence of prethermal discrete time crystals whose subharmonic response is entirely localized to zero-dimensional corner modes. Within the exponentially long prethermal regime, we show that the robustness of these corner modes arises from two related, yet distinct, mechanisms: the presence of a higher-order symmetry-protected topological phase in the effective Hamiltonian, or the emergence of a dynamical constraint that prevents the decay of the corner mode. While the first mechanism ensures the stability of the subharmonic response throughout the entirety of the prethermal regime, it is restricted to initial states in the ground state manifold of the effective Hamiltonian. By contrast, the second mechanism enables the observation of the prethermal time-crystalline order for arbitrary initial states, albeit with a timescale that is not only determined by the frequency of the drive, but also the relative energy scale across the system’s sublattices. We characterize these two mechanisms by simulating the dynamics of a periodically driven two-dimensional spin model, and discuss natural extensions of our model to all other dimensions.

Inspired by the primary goal of quantum thermodynamics—to characterize quantum signatures and leverage their benefits in thermodynamic scenarios—we design a work extraction task within a bipartite framework that exhibits a quantum thermodynamic advantage. The steerability of quantum correlations between the two parties is the key resource enabling such an advantage. In designing the task, we exploit the correspondence between steerability and the incompatibility of observables. Our work extraction protocol involves mutually unbiased bases, which exhibit maximum incompatibility and therefore maximum steerability, showcased in maximally entangled quantum states. The work extraction protocols consist of quenches and thermalization processes, which serve as fundamental building blocks for various thermodynamic protocols, such as heat engines. We derive upper bounds on the extractable work for unsteerable and steerable correlations and devise a protocol that saturates the latter. The ratio between the extractable work in steerable and unsteerable scenarios, which encapsulates the quantum advantage, increases with the dimension of the underlying system (sometimes referred to as an unbounded advantage). This proves a quantum thermodynamic advantage arising from steerable quantum correlations.

We show that a subset of the basis for the irreducible representations of a tensor-product SU(2) rotation forms a covariant approximate quantum error-correcting code with transversal U(1) logical gates. Generalizing previous work on “thermodynamic codes” to general local spin and different irreducible representations using only properties of the angular momentum algebra, we obtain bounds on the code inaccuracy under generic noise on any known $d$ sites, under independent and identically distributed noise, and under heralded $d$-local erasures. We demonstrate that this family of codes protects a probe state with quantum Fisher information surpassing the standard quantum limit when the sensing parameter couples to the generator of the U(1) logical gate.

Recent reports of cosmological parity violation in the four-point correlation function (4PCF) raise the question of how such violations could be systematically generated. Here we present a constructive procedure to generate arbitrary violations of vectorial and tensorial types on any scale, which is computationally efficient in the squeezed limit. We directly compute their numerical transfer function and find strong conservation in the linear regime. This procedure spans all squeezed parity-violating observables at the 4PCF following the quadratic estimator classification.

We report a study of the semileptonic decay $D^0\to {\overline{K}}^0{\pi }^{-}{\mu }^{+}{\nu }_{\mu }$ based on a sample of $7.9{\mathrm{fb}}^{-1}$ of $e^{+}{e}^{-}$ annihilation data collected at a center-of-mass energy of 3.773 GeV with the BESIII detector at the BEPCII collider. The branching fraction of the decay is measured for the first time to be $\mathcal{B}(D^0\to {\overline{K}}^0{\pi }^{-}{\mu }^{+}{\nu }_{\mu })=(1.373\pm 0.020_{\mathrm{stat}}\pm 0.023_{\mathrm{syst}})\%$, where the first uncertainty is statistical and the second is systematic. Based on the investigation of the decay dynamics, we find that the decay is dominated by the $K^{*}(892{)}^{-}$ resonance with the branching fraction measured to be $\mathcal{B}(D^0\to K^{*}(892{)}^{-}{\mu }^{+}{\nu }_{\mu })=(1.948\pm 0.033_{\mathrm{stat}}\pm 0.036_{\mathrm{syst}})\%$. We also determine the hadronic form factors for the $D^0\to K^{*}(892{)}^{-}{\mu }^{+}{\nu }_{\mu }$ decay to be $r_V=V(0)/A_1(0)=1.46\pm 0.11_{\mathrm{stat}}\pm 0.04_{\mathrm{syst}}$, $r_2=A_2(0)/A_1(0)=0.71\pm 0.08_{\mathrm{stat}}\pm 0.03_{\mathrm{syst}}$, and $A_1(0)=0.609\pm 0.008_{\mathrm{stat}}\pm 0.008_{\mathrm{syst}}$, where $V(0)$ is the vector form factor and $A_{1,2}(0)$ are the axial-vector form factors evaluated at $q^2=0$. The $A_1(0)$ is measured for the first time in $D^0\to K^{*}(892{)}^{-}{\mu }^{+}{\nu }_{\mu }$ decay. Averaging the form factor parameters that we reported previously in $D^0\to K^{*}(892{)}^{-}(\to {\overline{K}}^0{\pi }^{-})e^{+}{\nu }_e$ and $D^0\to K^{*}(892{)}^{-}(\to K^{-}{\pi }^0){\mu }^{+}{\nu }_{\mu }$ decays, we obtain $r_V=1.456\pm 0.040_{\mathrm{stat}}\pm 0.016_{\mathrm{syst}}$, $r_2=0.715\pm 0.031_{\mathrm{stat}}\pm 0.014_{\mathrm{stat}}$, and $A_1(0)=0.614\pm 0.005_{\mathrm{stat}}\pm 0.004_{\mathrm{syst}}$. This is the most precise determination of the form factor parameters to date measured in $D\to K^{*}(892)$ transitions, which provide the most stringent test on various theoretical models.