The interaction of light with correlated quantum matter in two-dimensional (2D) materials offers a powerful platform for exploring emergent quantum phenomena. Here, we report the realization of Landau polaritons in a monolayer tungsten diselenide (${\mathrm{WSe}}_2$) integrated into an optical microcavity. By embedding a two-dimensional electron gas (2DEG) in the monolayer and applying a perpendicular magnetic field, we achieve strong coupling between cavity photons and interband Landau level (LL) transitions, giving rise to hybrid light-matter quasiparticles. These Landau polaritons exhibit valley-dependent oscillations in the coupling strengths and resonance energies, driven by the electrical and magnetic filling of valley-contrasting Landau levels. Moreover, intervalley correlations between LL transitions and opposite-valley electrons lead to nonlinear renormalization of both LL transition energies and Landau-polariton coupling strengths. Our results establish a new paradigm for cavity quantum electrodynamics in correlated 2D systems and demonstrate control of Landau polaritons via the valley degree of freedom, opening new avenues for light-mediated manipulation of quantum phases.

Atomic force microscopy (AFM) with a functionalized tip can resolve the chemical structure of single molecules, but its application has been limited by slow imaging speeds and the restriction to constant-height operation. Here, we overcome these limitations by operating a Si cantilever in its second resonance mode, achieving exceptional force sensitivity. This enables robust, constant-height chemical-structure imaging at speeds up to 200 nm/s—over 60 times faster than previously reported. The enhanced sensitivity also resolves molecular bonds directly in constant-frequency-shift topographic images, a mode crucial for studying nonplanar systems. Our approach significantly expands the capabilities of AFM, opening new avenues for investigating the structure of three-dimensional molecules and tracking the dynamics of on-surface chemical reactions.

We implement a quantum neural network on trapped-ion and IBM superconducting quantum computers for Modified National Institute of Standards image classification. Feedforward is realized through qubit rotations conditioned on measurement outcomes from previous layers. The network is trained classically, while inference is performed experimentally on quantum hardware. A tunable interpolation parameter connects the classical and quantum regimes. Moderate values improve classification performance by introducing measurement uncertainty. For borderline images misclassified classically but correctly identified quantum mechanically, we observe strong deviations from idealized simulations due to physical noise, consistent with fluctuations between nearby minima in the classification landscape. We further benchmark noise by inserting additional single- and two-qubit gate pairs into the circuits. Our results motivate more complex quantum neural networks on noisy intermediate-scale quantum devices and suggest a possible route toward classically nonsimulable architectures.

Understanding dissipation in topological insulators is key to both fundamental physics and applications in spintronics, quantum computing, and low-power devices. Contrary to conventional expectations, dissipation in topological insulators need not rely on backscattering or dephasing: we show that finite-frequency local shot noise couples to the electromagnetic environment and generates near-field radiation, creating a nonlocal loss channel even at quantized conductance with vanishing global shot noise. Using a nonequilibrium Green’s-function framework, we link the local noise tensor to the spectral Poynting vector and compute persistent local noise in realistic two- and three-probe quantum Hall/quantum anomalous Hall interfaces where inequivalent edge modes overlap. This produces near-field “hot spots” measurable by scanning microscopy. We also give a design criterion: enforce spin-sector orthogonality to eliminate edge-mode overlap, thereby suppressing this loss channel. Our results provide a microscopic mechanism for hidden dissipation and a practical blueprint for diagnosing and reducing energy loss in topological electronics.

Inspired by the recent experimental discovery of superconductivity emerging from a time-reversal symmetry-breaking normal state in tetralayer rhombohedral graphene, we here investigate superconducting instabilities in this system. We classify the possible pairing instabilities, including states with commensurate and incommensurate center of mass momenta. As rotational symmetry is broken in the latter type of pairing states, their momentum-space structure is most naturally characterized by a “valley-independent Chern number,” measuring the relative chirality between the normal and superconducting state. We further demonstrate that superconductivity can condense at multiple incommensurate momenta simultaneously, leading to the spontaneous formation of a translational-symmetry-breaking superlattice superconductor. Studying multiple different pairing mechanisms and varying the degree of spin and valley polarization in the normal state, we compare the energetics of these superconductors. Our results demonstrate that valley-imbalanced rhombohedral tetralayer graphene can give rise to rich superconducting phenomenologies.

The Sachdev-Ye-Kitaev (SYK) model has attracted widespread attention due to its relevance to diverse areas of physics, such as high temperature superconductivity, black holes, and quantum chaos. The model is, however, extremely challenging to realize experimentally. In this Letter, we show how a particular form of Floquet engineering, termed “kinetic driving,” effectively eliminates single-particle processes and creates quasirandom all-to-all interactions when applied to models of Hubbard type. For the specific case of the Bose-Hubbard model, we explicitly verify that the driven system indeed reproduces SYK physics by direct comparison of the spectral form factor and out-of-time ordered correlation functions. Our findings indicate that a cold-atom realization of kinetic driving—achieved through modulation of hopping amplitudes in an optical lattice—offers a practical and accurate platform for quantum simulation of the SYK model.

The excess entropy scaling law is an empirical yet powerful structure-dynamics relationship for liquids and glasses. Here, we report the first experimental study that extends this entropy scaling concept to spin lattices, a fundamentally different class of disordered matter. We employ an in situ controlled buckled colloidal monolayer, which serves as a classical two-dimensional Ising lattice. Across isotropic compression, shear, and attraction-tuning experiments, the data reveal an exponential relationship, ${\tau }_{\alpha }\propto \exp (c{S}_{\mathrm{em}})$, between the spin relaxation time ${\tau }_{\alpha }$ and eigenmicrostate entropy $S_{\mathrm{em}}$, both derived from effective spin configurations. The control protocol dependent factor $c$ reflects the distinct ordering mechanisms and thermodynamic routes associated with each control experiment. This Letter identifies an entropy scaling framework for predicting dynamical properties of spin models using their spin configurations.

URhSn exhibits successive phase transitions at $T_{\mathrm{O}}=54\mathrm{K}$ and $T_{\mathrm{C}}=16\mathrm{K}$. While the transition at $T_{\mathrm{C}}$ is known to be ferromagnetic, the nature of the intermediate phase between $T_{\mathrm{O}}$ and $T_{\mathrm{C}}$ has remained elusive. Here, we report ${}^{117}\mathrm{Sn}$ nuclear magnetic resonance (NMR) measurements on high-quality single crystals of URhSn, which reveal NMR line splittings indicative of symmetry breaking in the intermediate phase. The field-direction and site dependences of these splittings are consistent with antiferroquadrupolar ordering characterized by the space group $P321$ (No. 150). This finding confirms the emergence of a novel form of chiral order driven by electronic degrees of freedom, without an underlying chiral crystal structure in URhSn.

Using $(10087\pm 44)\times {10}^6$ $J/\psi$ events collected with the BESIII detector at the BEPCII collider at the center-of-mass energy of $\sqrt{s}=3.097\mathrm{GeV}$, we report the first search for $\eta \to {\pi }^{0}S\to {\pi }^0\chi \overline{\chi }$ with $S$ denoting an on-shell dark scalar boson and $\chi$ an invisible dark matter particle. No significant signals are observed with $S$ mass ranging from 0 to $400\mathrm{MeV}/c^2$. The upper limits on the branching fractions and the new physics coupling strengths between $S$ and quarks are set to be $(1.8–5.5)\times {10}^{-5}$ and $(1.3–3.2)\times {10}^{-5}$ at the 90% confidence level, respectively. The constraints on the dark-matter-nucleon scattering cross section is improved by approximately five orders of magnitude over previous dark-matter-nucleon scattering experiments, providing unique insights into sub-GeV dark matter.

Quantum-entangled states underpin many emergent phenomena in quantum materials, yet their direct experimental identification remains a challenge. ${\mathrm{NiPS}}_3$, a van der Waals antiferromagnet exhibiting a resolution-limited magnetic exciton in its ordered phase, has been proposed to host a many-body entangled Zhang-Rice triplet state. Here, using ${}^{33}\mathrm{S}$ nuclear magnetic resonance (NMR) on ${}^{33}\mathrm{S}$-enriched ${\mathrm{NiPS}}_3$ single crystals, we provide microscopic evidence for this charge-transfer state. The ${}^{33}\mathrm{S}$ and ${}^{31}\mathrm{P}$ Knight shifts as a function of temperature reveal a unified spin-triplet configuration arising from strong hybridization between a self-doped hole in the S $3p$ orbitals and a hole in Ni $3d$ orbitals. Furthermore, the ${}^{33}\mathrm{S}$ nuclear spin-lattice relaxation rate exhibits a power-law divergence as it approaches the Néel temperature $T_N=155\mathrm{K}$, indicating critical slowing down of collective charge fluctuations consistent with spin-nematic correlations. These results reveal a spin-charge-intertwined ground state and establish the microscopic foundation for the exceptional coherence of the magnetic exciton in ${\mathrm{NiPS}}_3$.

Although the absorption of light in a bulk homogeneous semiconductor produces photocarriers with nonzero momenta, it generally does not produce a current in the absence of an applied electric field because equal amounts of carriers with opposite momenta are injected. The interference of absorption processes, for example, between one-photon and two-photon absorption can produce a current because constructive interference for carriers with one momentum can correspond to destructive interference for carriers with the opposite momentum. We show that for the interference between two-photon and three-photon absorption, the current has a narrower angular spread, i.e., a “beam” of electrons in a specified direction is produced in the semiconductor.

The time-dependent $CP$ asymmetry in $B^0\to J/\psi \rho (770{)}^0$ decays is measured using proton-proton collision data corresponding to an integrated luminosity of $6{\mathrm{fb}}^{-1}$, collected with the LHCb detector at a center-of-mass energy of 13 TeV during the years 2015–2018. The $CP$-violation parameters for this process are determined to be $2{\beta }_{c\overline{c}d}^{\mathrm{eff}}=0.710\pm 0.084\pm 0.051\mathrm{rad}$ and $|\lambda |=1.019\pm 0.034\pm 0.024$, where the first uncertainty is statistical and the second systematic. This constitutes the first observation of time-dependent $CP$ violation in $B^0\to J/\psi \rho (770{)}^0$ decays. Assuming approximate SU(3) flavor symmetry, these results are combined with the previous consistent LHCb measurement to set the most stringent constraint on the penguin contribution, $\mathrm{\Delta }{\varphi }_s$, to the $CP$-violating phase ${\varphi }_s$ in $B_s^0\to J/\psi \varphi (1020)$ decays, yielding $\mathrm{\Delta }{\varphi }_s=5.0\pm 4.6\mathrm{mrad}$.

An elementary particle such as a photon cannot be cut in two pieces. Still it must be possible to truncate a photon with an optical shutter. The result is neither another photon nor a mix of a photon and a vacuum. Instead it is a superposition and mix of photon numbers up to infinity. This state is rather complicated, but nevertheless locally equivalent to a single photon or vacuum to the left and right, respectively, of a narrow transition region.

We uncover a class of nonlinear odd viscoelastic effects in three spatial dimensions. We show that these dissipationless effects arise upon combining geometric distortions in two orthogonal directions, yielding momentum flow in the third direction. We demonstrate that the effect arises from nontrivial geometric tensors in quantum states, and can be scaled up with integer topological invariants. We further show that the effect fingerprints the multiband Hilbert-space geometry of the underlying quantum states, as encoded in the nonmetricity and three-state quantum geometric tensors. Our findings unravel the role of multistate geometry in viscoelastic phenomena, paving a path for experimental observation of uncharted nonlinear odd viscoelastic responses in quantum systems.

We report an unprecedented hidden density-wave instability in the trimer-based ruthenate ${\mathrm{Ba}}_4{\mathrm{Ru}}_3{\mathrm{O}}_{10}$, previously regarded as a purely antiferromagnetic insulator. This instability develops in two distinct stages: an electronically driven reconstruction at $T_{\mathrm{A}}=100\mathrm{K}$ manifested in structural, thermodynamic, and transport anomalies that remain remarkably insensitive to magnetic fields up to at least 14 T, followed only at much lower temperatures $T^{*}\sim 20\mathrm{K}$ by the emergence of strongly nonlinear transport. Below $T^{*}$, charge conduction exhibits distinct depinning thresholds, sharp negative differential resistance, and unusually slow collective dynamics in the Hertz range. Direct measurements show that Joule heating is negligible, and all nonlinear signatures vanish upon only 3% Ir substitution for Ru, demonstrating the intrinsic origin. These results identify ${\mathrm{Ba}}_4{\mathrm{Ru}}_3{\mathrm{O}}_{10}$ as a rare correlated system hosting a strongly pinned collective electronic mode intertwined with antiferromagnetism.

We introduce the pushy random walk, where a walker can push multiple obstacles, thereby penetrating large distances in environments with finite obstacle density. This process provides a minimal model for experimentally observed interactions of active particles with dense, deformable media. Using scaling arguments and numerical simulations, we show that in one dimension the walker carves out an obstacle-free cavity whose length grows subdiffusively with time. In two dimensions, increasing obstacle density drives a transition from free diffusion to localized behavior, where the walker is trapped within a cavity whose radius again grows subdiffusively with time. These results show how tracer-induced rearrangements qualitatively reshape transport in crowded media.

Chiral active materials are abundant in nature, including the cytoskeleton with attached motor proteins, rotary clusters of bacterial flagella, and self-spinning starfish embryos. These materials break both time reversal and mirror-image (parity) symmetries due to injection of torques at the microscale. It was recently discovered that chiral active materials show a new type of elastic response termed “odd” elasticity. Currently, odd elasticity is understood microscopically only in ordered structures, e.g., lattice designs of metamaterials. It remains to explore how odd elasticity emerges in natural or biological systems, which are usually disordered. To address this, we propose a minimal generic model for disordered “odd solids,” using micropolar (Cosserat) elasticity in the presence of local active torques. We find that odd elasticity naturally emerges as a nonlinear effect of internal particle rotations. Exploring the viscoelasticity of such a solid, when immersed in an odd fluid, we discover new dynamically unstable regions driven by the odd solid-fluid coupling and, in the underdamped regime, also by inertia. Remarkably, in the overdamped limit, this odd solid-fluid coupling allows for bulk wave propagation near these unstable regions.

A terrestrial population of room-temperature millicharged particles can arise if they make up a dark matter subcomponent or if they are light enough to be produced in cosmic ray air showers. In a companion paper, we showed that a simple electrified shell acts as an efficient accumulator for such particles, parametrically enhancing their local density by many orders of magnitude. Here we demonstrate that Cavendish tests of Coulomb’s Law, performed since the late 18th century, function as both quasistatic accumulators and detectors for this overdensity. Reinterpretations of these past Cavendish tests thus provide some of the strongest bounds on a terrestrial millicharge population. We also propose surrounding a Cavendish test with an additional charged shell, which significantly improves the sensitivity and can even enable detection of the irreducible density of millicharged particles generated from cosmic rays. Using decades-old technology, this can outperform future accelerator searches for sub-GeV masses.

Gravitational waves (GWs) in the $0.01\sim 1\mathrm{Hz}$ band encode unique signatures of the early Universe and merging compact objects, but they are beyond the reach of existing observatories. Theoretical models suggest that the Moon could act as a resonant detector, but the unknown influence of its rugged surface and heterogeneous interior poses a challenge to the accurate modeling of its response. Here, we address this long-standing uncertainty by constructing the first high-resolution, two-dimensional model of the lunar GW response, more realistic than previous ones. We achieve this by combining high-fidelity spectral-element simulations with the analytical power of normal-mode perturbation theory, thereby resolving topographical effects down to 2 km grid spacing while maintaining the capacity to discern global free-oscillation patterns. This dual-methodology approach not only recovers the expected predominant quadrupole ($l=2$) oscillation mode, but also exposes a systematic signal amplification in thick-crust regions. This enhancement is traced by our normal-mode analysis to a mode-coupling process, in which the original quadrupolar oscillation induced by the passing GW distributes energy into a series of higher-order modes, the hybridized eigenmodes of a laterally heterogeneous Moon. In certain narrow frequency ranges, we observe up to tenfold amplification spanning into the deci-hertz band, highlighting the power of numerical simulations in resolving these structurally fine-tuned features for designing future detectors. Our Letter establishes the Moon as a resonant GW detector albeit its complex topographical structures, and the resulting amplification maps provide a quantitative guide for the optimal landing site selection.

The recent success of gravitational-wave (GW) astronomy together with renewed plans for lunar geophysical instrumentation has revived interest in using the Moon as a resonant detector for midfrequency (mHz–Hz) GWs. In realistic observational scenarios, the GW strain amplitude is expected to be constrained independently by networks of GW detectors, which motivates an inverse, tomographic question: to what extent can measurements of the Moon’s seismic response to known GWs be used to infer its internal structure? In this Letter, we develop a first-principles, perturbative framework that maps spherically symmetric perturbations of the elastic and density structure to measurable changes in observables, especially GW-driven modal amplitudes of the Moon. The formalism combines (i) a normal-mode representation of the elastic response, (ii) first-order perturbation theory for eigenvalues and eigenfunctions, and (iii) a linearized observation model that links frequency and amplitude observables to model parameters (bulk and shear moduli, density, and interface locations) and their perturbations. We show that the estimation errors of the Moon’s elastic parameters can be reduced by about an order of magnitude with observations of calibrated GWs.