We present a search for light dark matter particles through their interactions with atomic electrons and nucleons, utilizing PandaX-4T data with an effective exposure of $1.04\mathrm{tonne}·\mathrm{year}$ for ionization-only data and $1.20\mathrm{tonne}·\mathrm{year}$ for paired data. Our analysis focuses on the energy range (efficiency $>0.01$) of approximately 0.33 to 3 keV for nuclear recoils and from 0.04 to 0.39 keV for electronic recoils. We establish the most stringent constraints on spin-independent dark matter-nucleon interactions within a mass range of $2.5–5.0\mathrm{GeV}/c^2$, spin-dependent neutron-only interactions within $1.0–5.6\mathrm{GeV}/c^2$, and spin-dependent proton-only interactions within $1.0–4.1\mathrm{GeV}/c^2$. Their corresponding limits at $3\mathrm{GeV}/c^2$ are $1.1\times {10}^{-43}$, $8.4\times {10}^{-40}$, and $2.8\times {10}^{-38}{\mathrm{cm}}^2$, respectively. Additionally, our results improve the upper limits on the dark matter-electron scattering cross section by a factor of 1.5 and 9.3 for heavy and light mediator scenarios, respectively, within $50\mathrm{MeV}/c^2$ to $10\mathrm{GeV}/c^2$, compared with previous best results. The improved limits reach $1.5\times {10}^{-41}$ and $5.6\times {10}^{-37}{\mathrm{cm}}^2$ at $200\mathrm{MeV}/c^2$ for the heavy and light mediators, respectively.

When embedded in superfluid helium nanodroplets, the dopant molecule exhibits either localization or delocalization behaviors that are critically determined by the spatial spread of its wave function, which in turn are influenced by the confining potential of the nanodroplets. Here, we examine the spatial extent of a molecule’s wave function with respect to the size of the nanodroplet by diagnosing the angular nodal structures in the photoelectron momentum distributions (PMDs). We find that, for the lightest ${\mathrm{H}}_2$ molecules or heavier ${\mathrm{D}}_2$ and ${\mathrm{O}}_2$ molecules, with extents of wave function distributions comparable to or smaller than the nanodroplet size, the emitted electrons undergo either minimal or significant scattering with the liquid helium surroundings, leading to either preserved or blurred nodal structures in the PMDs. These observations reveal the underlying delocalization or localization of a molecule within the nanodroplet, which is governed by its wave functions as determined by the confining potential of the droplet. Our findings provide insight into the quantum solvation dynamics of light impurities in nanoscale and confined systems.

The concept of flux in quantum physics is connected to many intriguing phenomena such as the Aharonov-Bohm effect and Hofstadter butterfly. Particularly, flux in lattices with certain symmetries gives rise to many unprecedented phases of matter. Here, we report the experimental realization of two-dimensional photonic crystals featuring diverse synthetic $\pi$-flux patterns, achieved through harnessing the higher-orbital degree of freedom within confined-Mie-resonance photonic crystals. As a proof of concept, we fabricate two types of $\pi$-flux photonic crystals, and show that novel topological phases can emerge with peculiar optical effects, including a topological edge state with $4\pi$-period phase evolution, as well as two pairs of topological states which are localized at opposite boundaries but related by a nonlocal twist. These signatures characterize unambiguously a photonic Möbius insulator [an insulator with topological edge states with a $4\pi$-periodic sideband junction (like a Möbius ring)] and a momentum-space-nonsymmorphic symmetry characterized insulator, which remain experimentally unexplored to date. Our Letter opens the frontiers to explore the underlying physics between synthetic $\pi$-flux and photonic crystals.

We investigated ultrafast defect-lattice dynamics in diamond using the ${\mathrm{N}}_{\mathrm{s}}:{\mathrm{H}\text{−}\mathrm{C}}^0$ defect, an analog of bond-centered hydrogen in semiconductors. Combining synthesis, ultrafast vibrational spectroscopy, and ab initio calculations, we show that excitation of the defect’s stretch mode leads to the generation of localized phonons and the formation of a hot ground state, where the interatomic potential is transiently modified. Our results reveal unexpected nonequilibrium phonon effects despite diamond’s exceptionally high thermal conductivity, with implications for quantum defect engineering.

While hydrodynamic coupling has long been considered essential for synchronization of eukaryotic flagella, recent experiments on the unicellular biflagellate model organism Chlamydomonas demonstrate that -at the single cell level- intracellular mechanical coupling is necessary for coordination. It is therefore unclear what role, if any, hydrodynamic forces actually play in the synchronization of multiple flagella within individual cells, arguably the building block of large scale coordination. Here we address this question experimentally by transiently blocking hydrodynamic coupling between the two flagella of single Chlamydomonas. Our results reveal that in wild type cells intracellularly mediated forces are necessary and sufficient for flagellar synchronization, with hydrodynamic coupling causing minimal changes in flagellar dynamics. However, fluid-mediated ciliary coupling is responsible for the extended periods of anti-phase synchronization observed in a mutant with weaker intracellular coupling. At the single-cell level, therefore, flagellar coordination depends on a subtle balance between intracellular and extracellular forces.

While the spin-ice state of bulk pyrochlores such as ${\mathrm{Dy}}_2{\text{Ti}}_2{\mathrm{O}}_7$ and ${\mathrm{Ho}}_2{\text{Ti}}_2{\mathrm{O}}_7$ has been extensively studied in the past several decades due to its unique degenerate ground state and emergent monopole excitation, whether it survives in the thin-film form remains a mystery. The limited volume of the thin-film sample makes it challenging to study the intrinsic magnetic properties. Here, we synthesized 18-nm-thick ${\mathrm{Dy}}_2{\text{Ti}}_2{\mathrm{O}}_7$ thin film on yttria-stabilized zirconia with $9.5\mathrm{mol}\%{\mathrm{Y}}_2{\mathrm{O}}_3$ substrate and capped it by a thin conductive ${\mathrm{Bi}}_2{\text{Ir}}_2{\mathrm{O}}_7$ layer and performed the proximitized magnetoresistance measurements. Our Letter found that the ice-rule-breaking phase transition survives but with a modified effective nearest-neighbor interaction ($J_{\mathrm{eff}}=1.054\mathrm{K}$) and distorted Ising spin axes ($\epsilon =+0.051$) compared to the bulk crystal. The results are supported by the simultaneously measured capacitive torque magnetometry. Our Letter demonstrates that proximitized transport is an effective tool for thin films of insulating frustrated magnets.

Altermagnets are a novel class of magnetic materials with cutting-edge advantages. Identifying altermagnets, i.e., exploring their distinguishing fingerprints, is vital but challenging. The as-reported spontaneous anomalous Hall effect is not universally present in all altermagnets due to magnetic symmetry constraints, and the second-order nonlinear Hall effect is prohibited by spatial-inversion symmetry. Here, we report the experimental discovery of a third-order nonlinear Hall effect (TNHE) in ${\text{RuO}}_2$ thin films. TNHE emerges when current is applied along [110] or $[\overline{1}10]$ crystal direction for ${\text{RuO}}_2(001)$, as the second-order currents induce a magnetization by breaking orthogonal mirror and rotation symmetries of this altermagnet. These symmetry-breaking conditions also enforce a twofold angular dependence of TNHE concerning current direction in the ${\text{RuO}}_2(001)$ plane. Moreover, temperature-dependent measurements and scaling law analysis reveal that TNHE is governed primarily by the third-order skew scattering mechanism. Our findings establish TNHE as a transport fingerprint of altermagnet ${\text{RuO}}_2$, which can be generalized to other altermagnets such as $d$-wave ${\mathrm{V}}_2{\mathrm{X}}_2\mathrm{O}$ ($\mathrm{X}=\text{Se}$ or Te) and $g$-wave MnTe and CrSb.

Conformal transformation is a powerful paradigm for designing isotropic metamaterials with significant practical value. However, conventional conformal transformation faces challenges in achieving precise multiphysics control, specifically for the concurrent regulation of thermal and electromagnetic fields. This difficulty arises because the interface matching mechanisms for dissipative thermal fields and nondissipative electromagnetic fields are fundamentally different. To overcome these challenges, we propose a common design paradigm for multiphysics-applicable interface matching, based on rescaled Schwarz-Christoffel transformation (RSCT). This framework leverages the Schwarz-Christoffel transformation—a conformal map between polygonal domains that intrinsically directs energy flow—and integrates it with rescaling techniques that enable the redistribution of energy flow density. By simultaneously controlling energy flow and energy flow density, two key quantities that can be manipulated in both thermal and electromagnetic fields, RSCT establishes a general platform for perfect interface matching using solely isotropic media. Employing RSCT, we design and experimentally validate three energy-flow regulators: expanders, guiders, and cloaks. Furthermore, the inherent capability of RSCT to form devices of arbitrary polygonal shapes makes it highly compatible with the layout of integrated circuits, holding great promise for coordinated signal and heat management in such systems.

We experimentally realize a quantum clock by using a charge sensor to count charges tunneling through a double quantum dot (DQD). Individual tunneling events are used as the clock’s ticks. We quantify the clock’s precision while measuring the power dissipated by the DQD and, separately, the charge sensor in both direct-current and radio-frequency readout modes. This allows us to probe the thermodynamic cost of creating ticks microscopically and recording them macroscopically. Our experiment is the first to explore the interplay between the entropy produced by a microscopic clockwork and its macroscopic measurement apparatus. We show that the latter contribution not only dwarfs the former but also unlocks greatly increased precision, because the measurement record can be exploited to optimally estimate time even when the DQD is at equilibrium. Our results suggest that the entropy produced by the amplification and measurement of a clock’s ticks, which has often been ignored in the literature, is the most important and fundamental thermodynamic cost of timekeeping at the quantum scale.

Creating and manipulating anyons and symmetry defects in topological phases, especially those with a non-Abelian character, constitutes a primitive for topological quantum computation. We provide a physical protocol for implementing the ribbon operators of non-Abelian anyons and symmetry defects. We utilize dualities, in particular, the Kramers-Wannier or gauging map, which have previously been used to construct topologically ordered ground states by relating them to simpler states. In this Letter, ribbon operators are implemented by applying a gauging procedure to a lower-dimensional region of such states. This protocol uses sequential unitary circuits or, in certain cases, constant-depth adaptive circuits. We showcase this for anyons and defects in the ${\mathbb{Z}}_3$ toric code and $S_3$ quantum double. The general applicability of our method is demonstrated by deriving unitary expressions for ribbon operators of various (twisted) quantum doubles.

We show that the amplitude of electromagnetic memory can be significantly enhanced in comparison to known estimates. In a Lorentz breaking phase of lowered phase velocity of light, there exist critical spacetime directions of memory-source emission along the effective light cone, about which the total memory offset receives order of magnitude increases. The same amplification is already present in the Lorentz preserving case by considering ultrarelativistic memory-source charges. These observations may pave the way for a first observation of the phenomenon of memory and laboratory tests of the concepts of asymptotic symmetries and soft theorems.

We use charge sensing to detect entropy changes in a double quantum dot defined by electrostatic gating of a GaAs/AlGaAs heterostructure. This system can be tuned to be two separate systems, like two independent, artificial atoms, or a single coherent system, like a molecule. We study entropy changes in both regimes due to changes in the occupation of the system. First, we recover the single-dot result for each dot, that the occupation of the dot by a single electron corresponds to an increase in the entropy of $k_{\mathrm{B}}\log 2$. Next, we examine two different charge transitions in the “molecular” regime and how it reveals itself in terms of the measured entropy. We also uncover a realization of Pauli blockade that clutters the entropy signal. By applying a rate equation model, we demonstrate the effect’s nonequilibrium origins and exclude it from the analysis of the system’s entropy. Understanding these experiments in this simplest coupled system enables the study of the entropy in other, more complicated coupled quantum systems, such as ones with topological or highly entangled ground states.

Frustration is a key driver of exotic quantum phases, yet its role in charge dynamics remains largely unexplored. We show that charge frustration—induced by electronic polarization effects—stabilizes unconventional insulating states in the one-dimensional extended Hubbard model. Using exact diagonalization and density-matrix renormalization group, we uncover a charge-disordered phase that remains insulating despite lacking long-range order and possessing an effectively attractive on-site interaction—a behavior reminiscent of gapful spin liquids in frustrated spin systems. We also identify a fragile ferroelectric phase and a charge-density-wave state with emergent eight-site periodicity. These findings establish charge frustration, driven by charge-dipole interactions, as a robust mechanism for realizing exotic phases in low-dimensional correlated systems, with implications for organic conductors, transition-metal oxides, and ultracold polar molecules.

The Thouless pump, a cornerstone of topological physics, enables unidirectional quantized wave or particle transport via geometric Berry phase engineering in periodically driven systems. While decades of research have been dedicated to monopole-mediated pumping, mechanisms governed by higher-order singularities like Berry dipoles remain unexplored. Here, we report on the experimental demonstration of a Berry-dipole-mediated returning Thouless pump (RTP) in a 1D acoustic waveguide array achieved through adiabatic encircling of a Berry dipole singularity. During this adiabatic cycle, an initial edge-localized mode first delocalizes into the bulk and eventually returns to the original edge, marking the characteristic signature of the RTP. Notably, this RTP exhibits an interesting feature of pseudospin flipping. The demonstrated RTP contrasts sharply with the well-studied monopole-governed pumps that feature unidirectional transport.

We report the creation of ultracold samples of ${{}^{39}\mathrm{K}}^{133}\mathrm{Cs}$ molecules in their rovibrational ground state. By investigating potentially suitable excited states using one- and two-photon spectroscopy, we have identified a pathway to the ground state via an exceptionally narrow intermediate state. Using stimulated Raman adiabatic passage, we create trapped samples of up to 3500 molecules at temperatures of $1\mathrm{\mu }\mathrm{K}$ with one-way efficiencies of 71%. The lifetime of these samples is limited by a near-universal two-body loss process, which could shed new light on similar loss mechanisms in other molecular species. Our results are a step toward establishing an alternative molecular species as a platform for the study of bosonic and fermionic quantum matter with strong dipolar interactions.

We present the first benchmark measurements of oxygen opacity at high-energy-density, crucial for understanding stellar interiors. A $3–5\text{−}\mathrm{\mu m}$ thick ${\text{SiO}}_2$ sample was heated using a Z facility x-ray source, and opacity was measured in the $5–19.5\AA$ range with multiple spectrometers. The electron temperature and density inferred from Si $K$-shell spectra were $148\pm 4\mathrm{eV}$ and $8.6\pm 1.4\times {10}^{21}{\mathrm{cm}}^{-3}$, respectively. Six experiments showed opacity reproducibility within $\pm 15\%$ and 5%–25% opacity uncertainty. Measured oxygen opacity and seven different opacity models exhibit extraordinary overall agreement. Discrepancies near the H-like photon ionization threshold and in certain spectral lines suggest the need for model refinements.

Conventional phase transitions in two-dimensional (2D) materials typically involve gradual and progressive structural evolution upon external stimuli. However, analogous to the latent heat phenomena in classical thermodynamics, where energy absorption leads to internal reconfiguration without immediate phase change, we report an unconventional “latent phase transition” in 2D palladium diselenide (${\mathrm{PdSe}}_2$), uncovered through in situ atomic scanning transmission electron microscopy. During Pd atom implantation and subsequent thermal annealing, the ${\mathrm{PdSe}}_2$ lattice absorbs input energy without significant structural rearrangement, maintaining its original framework over an extended temperature range. Remarkably, once a critical threshold of internal chemical pressure is reached, the structure abruptly collapses into a three-dimensional crystalline ${\mathrm{Pd}}_{17}{\mathrm{Se}}_{15}$ phase. Stabilized by the robust layer structure of ${\mathrm{PdSe}}_2$, this phase transition behavior closely mirrors the latent energy and sudden transformation characteristic of classical latent heat processes. Density functional theory calculations corroborate the mechanism, highlighting the role of van der Waals gap energy buffering and the weak $\mathrm{Pd}-\mathrm{Pd}$ interactions. Our findings establish an unusual phase transition paradigm in 2D materials, enriching the fundamental understanding of phase engineering in low-dimensional systems.

Controlling and monitoring interfacial chemical reactions is crucial for electrochemistry and photochemistry. Here, we developed a new type of interface-sensitive magnetic resonance technique by combining qPlus-based scanning probe microscopy (SPM) and quantum sensing based on a single nitrogen-vacancy center near the surface of a diamond. Using this technique, we investigated water dissociation at the hydrophilic diamond surface and monitored its elementary steps, including electron transfer, bond breaking, as well as water and hydrogen diffusion. The SPM tip was used to locally inject electrons into the interfacial water, and the resulting hydrated electrons (${\mathrm{e}}_{(\mathrm{aq})}^{-}$) were found to have specific configurations at the interface with a hyperfine interaction of about 28 MHz, which agrees with density-functional theory calculations. We observed that ${\mathrm{e}}_{(\mathrm{aq})}^{-}$ can induce water dissociation and the reaction product hydroxides diffuse $\sim 2.3$ times faster than water molecules. The diffusion coefficients of water and the reaction product hydroxides at the interface are about 3 orders of magnitude smaller than those in the bulk phase, but their ratio almost remain the same. These results show that the combination of SPM and quantum sensing provides a new platform to reveal the detailed electronic and nuclear processes of interfacial chemical reactions with nanometer resolution.

Optical atomic clocks with unrivaled precision and accuracy have advanced the frontier of precision measurement science and opened new avenues for exploring fundamental physics. A fundamental limitation on clock precision is the standard quantum limit (SQL), which stems from the uncorrelated projection noise of each atom. State-of-the-art optical lattice clocks interrogate large ensembles to minimize the SQL, but density-dependent frequency shifts pose challenges to scaling the atom number. The SQL can be surpassed, however, by leveraging entanglement, though it remains an open problem to achieve quantum advantage from spin squeezing at state-of-the-art stability levels. Here, we demonstrate clock performance beyond the SQL, achieving a fractional frequency precision of $1.1\times {10}^{-18}$ for a single spin-squeezed clock. With cavity-based quantum nondemolition measurements, we prepare two spin-squeezed ensembles of $\sim 30000$ strontium atoms confined in a two-dimensional optical lattice. A synchronous clock comparison with an interrogation time of 61 ms achieves a metrological improvement of 2.0(2) dB beyond the SQL, after correcting for state preparation and measurement errors. These results establish the most precise entanglement-enhanced clock to date and offer a powerful platform for exploring the interplay of gravity and quantum entanglement.

Gas bubble accumulation on substrates reduces the efficiency of many physicochemical processes, such as water electrolysis. For microbubbles, where buoyancy is negligible, coalescence-induced jumping driven by the release of surface energy provides an efficient pathway for their early detachment. At the nanoscale, however, gas compressibility breaks volume conservation during coalescence, suppressing surface energy release and seemingly disabling this detachment route. Using molecular dynamics simulations, continuum numerical simulations, and theoretical analysis, we show that surface nanobubbles with sufficiently large contact angles can nevertheless detach after coalescence. In this regime, detachment is powered by the release of pressure energy associated with nanobubble volume expansion. This finding thus establishes a unified driving mechanism for coalescence-induced bubble detachment across all length scales.