Magneto-optical trapping of molecules has thus far been restricted to molecules with ${}^2\mathrm{\Sigma }$ electronic ground states. These species are chemically reactive and only support a simple laser cooling scheme from their first excited rotational level. Here, we demonstrate a magneto-optical trap (MOT) of aluminum monofluoride (AlF), a deeply bound and intrinsically stable diatomic molecule with a ${}^1{\mathrm{\Sigma }}^{+}$ electronic ground state. The MOT operates on the strong $A^1\mathrm{\Pi }\leftarrow X^1{\mathrm{\Sigma }}^{+}$ transition near 227.5 nm, whose $Q(J)$ lines are all rotationally closed. We demonstrate a MOT of about $6\times {10}^4$ molecules for the $J=1$ level of AlF, more than ${10}^4$ molecules for $J=2$ and 3, and with no fundamental limit in going to higher rotational levels. Laser cooling and trapping of AlF is conceptually similar to the introduction of alkaline-earth atoms into cold atom physics, and is key to leveraging its spin-forbidden $a^3\mathrm{\Pi }\leftarrow X^1{\mathrm{\Sigma }}^{+}$ transition for precision spectroscopy and narrow-line cooling.

We use a quantum-logic spectroscopy (QLS) protocol to control the quantum state of a ${\mathrm{CaH}}^{+}$ ion in a cryogenic environment in which reduced thermal radiation extends rotational state lifetimes by an order of magnitude over those at room temperature. By repeatedly and adaptively probing the molecule, detecting the outcome of each probe via an atomic ion, and using a Bayesian update scheme to quantify confidence in the molecular state, we demonstrate state preparation and measurement (SPAM) in a single quantum state with infidelity less than $6\times {10}^{-3}$ and measure Rabi flopping between two states with greater than 99% contrast. The protocol does not require molecule-specific lasers and can be generalized, paving the way for high-fidelity quantum control of many other molecular ions.

The energy spectrum of cosmic rays above 2.5 EeV has been measured across the declination range $-90°\le \delta \le +44.8°$ using $\sim 310000$ events accrued at the Pierre Auger Observatory from an exposure of $(104900\pm 3100){\mathrm{km}}^2\mathrm{sr}\mathrm{yr}$. No significant variations of energy spectra with declination are observed, after allowing or not for nonuniformities across the sky arising from the well-established dipolar anisotropies in the arrival directions of ultrahigh-energy cosmic rays. The instep feature in the spectrum at $\simeq 10\mathrm{EeV}$ reported previously is now established at a significance above $5\sigma$. Within the statistics, the energy spectra are indistinguishable across declinations so disfavoring an origin for the instep from a few distinctive sources.

We investigate the intercalation of epoxy resin into a Weyl semimetal, ${\mathrm{WTe}}_2$, by using a scanning tunneling microscopy. We show that intercalant molecules have self-similar height variations with the silver-mean quasiperiodicity and also that they create phason and soliton defects to yield a mean coherence length of 15 sequential order. In addition, we unravel that weak quasiperiodic potentials imposed by the intercalation layer drive a ${\mathrm{WTe}}_2$ surface to have an enhanced conductance near the Fermi level while keeping its semimetal phase, providing a direct verification of theoretical prediction.

Edge states reflect the key physical properties yet are difficult to probe individually, particularly when several states are present at an edge. We present momentum resolved tunneling spectroscopy between a quantum well and a quantum wire to extract the dispersions of the quantum Hall edge states. Momentum and energy selective tunneling allows for separately addressing the different states even if they are spatially overlapping. This delivers the edge state velocities over broad ranges of magnetic field and density, in excellent agreement with a hard wall model. This technique provides a basis for future edge state selective spectroscopy on quantum materials.

The Landau-Lifshitz-Gilbert (LLG) equation has been the cornerstone of modeling the dynamics of localized spins, viewed as classical vectors of fixed length, within nonequilibrium magnets. When light is employed as the nonequilibrium drive, the LLG equation must be supplemented with additional terms that are usually conjectured using phenomenological arguments for direct optomagnetic coupling between localized spins and (real or effective) magnetic field of light. However, direct coupling of magnetic field to spins is $1/c$ smaller than coupling of light and electrons; or both magnetic and electric fields are too fast for slow classical spins to be able to follow them. Here, we displace the need for phenomenological arguments by rigorously deriving an extended LLG equation via Schwinger-Keldysh field theory (SKFT). Within such a theory, light interacts with itinerant electrons, and then spin current carried by them exerts spin-transfer torque onto localized spins, so that when photoexcited electrons are integrated out we arrive at a spin-only equation. Unlike the standard phenomenological LLG equation with local-in-time Gilbert damping, our extended one contains a non-Markovian memory kernel whose plot within the plane of its two time arguments exhibits fractal properties. By applying the SKFT-derived extended LLG equation, as our central result, to a light-driven ferromagnet as an example, we predict an optically induced magnetic inertia term. Its magnitude is governed by a spatially nonlocal and time-dependent prefactor, leading to the excitation of coherent magnons at sharp frequencies in and outside of the band of incoherent (or thermal) magnons.

We study the snapping instability of a spherical elastic shell induced by a viscous flow, the umbrella flipping problem when life is at low Reynolds numbers. We combine precision desktop-scale experiments, fluid-structure simulations, shell theory, fluid mechanics, and scaling analysis to determine the instability threshold as a function of the geometrical and material parameters of the system. Building on these findings, we devise a snapping-based valve that passively and abruptly alters the hydraulic resistance of a channel, offering robust flow control without active components. Beyond the application, our Letter presents what we believe to be a prototypical example of fluid-induced elastic instability in viscous flow, providing a foundation for future explorations in soft hydraulics and flow-responsive structures.

Ultrastable glasses (USGs) exhibit strikingly different properties from liquid-cooled normal glasses (NGs), yet their molecular dynamics remain poorly understood. Using $\beta$-detected NMR of implanted spin-polarized ${}^8{\mathrm{Li}}^{+}$, we directly track the depth and temperature dependence of the $\gamma$ relaxation—phenyl ring twisting—in highly monodisperse atactic styrene oligomers. Near the bulk glass transition temperature $T_{\mathrm{g}}$, USGs show much faster surface dynamics but slower bulk dynamics than an NG. Cooling below $T_{\mathrm{g}}$ reveals a sharp crossover at $T^{*}$, where surface dynamics vitrify on tens to hundreds of nanosecond timescales and become slower than in the bulk. The NG further displays two distinct $T^{*}$ values near the surface, pointing to heterogeneous local structure. Despite these differences, all dynamics obey entropy-enthalpy compensation, suggesting a common molecular mechanism. These results show that preparation and thermal history lock styrene oligomeric glasses into distinct regions of the potential energy landscape, giving rise to fundamentally different glassy dynamics.

A quantum memory is an essential element for quantum computation, quantum networks, and quantum metrology. Previously, a single-qubit quantum memory with a coherence time of about an hour has been realized in a dual-species setup where a coolant ion provides sympathetic cooling for a memory ion of a different species. However, the frequent random position hopping between the ions in the room-temperature trap limits the technique to be applicable only to single-qubit storage. Here, we report a multi-ion quantum memory in a cryogenic trap based on the dual-type scheme and demonstrate a coherence time above two hours for a qubit encoded in the decoherence-free subspace, i.e., two-ion entangled states, after correcting the dominant leakage error. Our scheme alleviates the necessity of an ultrastable frequency reference for the stored qubit, and it has a preferable scalability owing to the same mass of the metastable-state memory ions and the ground-state coolant ion.

Altermagnets have been identified as the third category of magnetic materials, exhibiting momentum-dependent spin splitting characterized by even powers of momentum. In this Letter, we show that when subjected to elliptically polarized light, these materials serve as an exemplary framework for the dynamic generation of topological bands featuring higher-order spin-orbit coupling (SOC). Notably, while the generated Zeeman field remains invariant to the particular altermagnetic ordering, the induced higher-order SOCs are related to the magnitude and symmetry of the altermagnetic order. Specifically, we show that an altermagnet exhibiting ${\mathbf{k}}^{2n}$-spin splitting can generate odd-in-$\mathbf{k}$ spin-orbit couplings up to ${\mathbf{k}}^{2n-1}$. In the limit of circularly polarized light, the only correction is $k^{2n-1}$, with all lower-order contributions being nullified. Interestingly, light-induced SOCs significantly impact the low-energy band topology, where their Chern numbers change by $\mathrm{\Delta }C=\pm 1$, 2, 3 for $d$, $g$, $i$-wave altermagnets. Finally, we find a critical field in which a persistent spin texture is realized, a highly desirable state with predicted infinite spin lifetime. Our Letter showcases light as a powerful, controllable tool for engineering complex and exciting phenomena in altermagnets.

A search for the dimuon decay of the Higgs boson is presented based on $pp$ collision data recorded by ATLAS during Run 3 of the Large Hadron Collider, corresponding to an integrated luminosity of $165{\mathrm{fb}}^{-1}$ at $\sqrt{s}=13.6\mathrm{TeV}$. To enhance the sensitivity, the results are combined with those from Run 2. An excess of events over the background is observed with a significance of $3.4\sigma$ ($2.5\sigma$ expected). The best-fit signal strength is $\mu =1.4\pm 0.4$. This result provides evidence for the $H\to \mu \mu$ decay with ATLAS data and offers a direct probe of the Higgs-boson Yukawa coupling to second-generation fermions.

The observation of a wide peaking structure in the $B_c^{+}\gamma$ mass spectrum is reported using proton-proton collision data collected by the LHCb detector at center-of-mass energies of 7, 8, and 13 TeV, corresponding to a total integrated luminosity of $9{\mathrm{fb}}^{-1}$. The statistical significance over the background-only hypothesis exceeds seven standard deviations. The width of the observed structure is larger than the expectation from a single-peak hypothesis, and is well described by an effective minimal model consisting of two narrow peaks located at $6704.8\pm 5.5\pm 2.8\pm 0.3\mathrm{MeV}/c^2$ and $6752.4\pm 9.5\pm 3.1\pm 0.3\mathrm{MeV}/c^2$. The uncertainty terms are statistical, systematic, and associated to the knowledge of the $B_c^{+}$ mass, respectively. The measured peak locations are in line with theoretical predictions for lowest excited $P$-wave $B_c^{+}$ states, marking the first observation of orbitally excited beauty-charm mesons and providing important insights into the internal dynamics of hadrons containing two heavy quarks.

In 1927, during the fifth Solvay Conference, Einstein and Bohr described a double-slit interferometer with a “movable slit” that can detect the momentum recoil of one photon. Their debate centered on this Gedankenexperiment has provided profound insights into the central concepts of quantum mechanics. Despite many efforts to reproduce this conceptual experiment, a linear-optical version with a movable, quantum-limited slit and tunable momentum width remained challenging. Here, we report a realization of the Einstein-Bohr interferometer using a single atom in an optical tweezer, which is cooled to the motional ground state in three dimensions such that its momentum uncertainty is comparable to that of a single photon. We design an interferometric configuration where the single atom serves as an ultralight, quantum-limit beam splitter that is momentum entangled with the input photon. By varying the trap depth of the optical tweezer, we dynamically tune the atom’s intrinsic momentum uncertainty, thus enabling the observation of a gradual shift in the visibility of single-photon interference. The interferometer also allows us to distinguish the classical noise caused by atom heating from the quantum-limited noise due to the momentum transfer, illustrating a quantum-to-classical transition.

In 1914, Ramanujan unveiled 17 extraordinary infinite series for $1/\pi$. In this Letter, we uncover their physics origin by relating them to 2D logarithmic conformal field theories (LCFTs), which emerge in diverse settings such as the fractional quantum Hall effect, percolation, polymers, and even holography. Through this LCFT connection, we reinterpret such infinite series in terms of fundamental CFT data-the operator spectrum and OPE coefficients. This perspective leads to novel physics-inspired approximations for $1/\pi$. Drawing lessons from Ramanujan’s formulas, we construct a new family of bases for expanding LCFT correlators that converge far more rapidly than the standard conformal block decomposition. This is achieved using recently developed stringy/parametric crossing-symmetric dispersion relations. Remarkably, when working with these new expansions, the action of a certain differential operator (which arises naturally from the Ramanujan connection) dramatically enhances convergence, with the entire contribution collapsing to that of the logarithmic identity operator. This striking simplification hints at a universal property of LCFTs. Finally, we discuss a new holographic interpretation of this unexpected mathematics-physics connection.

A key challenge in ultrafast science has been to directly track the coupled motions of electrons and nuclei in real space and real time. This Letter presents a significant step toward this goal by demonstrating the feasibility of time-resolved real-space tracking of valence electron and hydrogen dynamics during the photodissociation of ammonia (${\mathrm{NH}}_3$) using MeV ultrafast electron diffraction. It is demonstrated that the enhanced temporal resolution, in conjunction with the analysis of the charge-pair distribution function, enables the disentanglement of the correlated motion of valence electrons and hydrogens in a photoexcited ammonia molecule. The methodology employed in this Letter, which utilizes the charge-pair distribution function from ultrafast electron scattering to retrieve intertwined electron and nucleus dynamics, may open up new opportunities in the study of quantum dynamics for a wide range of molecules.

One of the profound consequences of the fractional quantum Hall (FQH) effect is the notion of fractionally charged anyons. In spite of extensive experimental study, puzzles remain, however. For example, both shot-noise and Aharonov-Bohm interference measurements sometimes report a charge that is a multiple of the elementary charge. We report here high-precision microscopic calculations that reveal the surprising result that the FQH anyons often bind together into stable clusters, which we term molecular anyons. This is counterintuitive, given that the elementary anyons carry the same charge and are, therefore, expected to repel one another. The number of anyons in a cluster, its binding energy, and its size depend sensitively on the parent FQH state and the interaction between electrons (which is experimentally tunable, e.g., by varying the quantum well width). Our calculations further suggest that the charge-$1/4$ non-Abelian anyons of the $5/2$ FQH state may also bind to form charge-$1/2$ Abelian clusters. The existence of molecular anyons not only can provide a natural explanation for the observed charges, but also leads to a host of new predictions for future experiments and invites a reanalysis of many past ones.

Quantum Monte Carlo (QMC) methods offer exact solutions for quantum many-body systems but face severe limitations in fermionic systems like atomic nuclei due to the sign problem. While sign-problem-free QMC algorithms exist and provide valuable insights across disciplines, they have been restricted to simple models with limited quantitative predictive power. Here we overcome this barrier by developing a novel lattice nuclear force that is rigorously sign-problem-free for even-even nuclei. This interaction achieves a standard deviation of $\sigma =2.932\mathrm{MeV}$ from experimental binding energies for 76 even-even nuclei ($N,Z\le 28$), matching state-of-the-art phenomenological mean-field models. Key innovations include the first sign-problem-free implementation of spin-orbit coupling for shell evolutions and an efficient QMC-optimized framework for global parameter fitting. Using this approach, we compute binding energies from ${}^4\mathrm{He}$ to ${}^{132}\mathrm{Sn}$ with unprecedented one-thousandth level numerical precision, reproduce symmetric nuclear matter saturation, and reveal novel spin-orbit-driven clustering in light nuclei. This Letter transforms sign-problem-free QMC simulation into a scalable and predictive nuclear structure tool, while establishing a high-fidelity, nonperturbative foundation for ab initio calculations of heavy nuclei.

Multiferroics are known to be classified into two types. However, type I lacks sufficient magnetoelectric coupling and type II lacks sufficient electric polarization, making both practically difficult. In this Letter, we explore the possibility of type-III multiferroics, where the origins of ferroelectricity and magnetism are highly intertwined but not causally related, with a combination of strong magnetoelectric coupling and large polarization. Our first-principles calculations predict that monolayer ${\mathrm{TiCdO}}_4$ is such a type-III ferroelectric-ferromagnetic multiferroic with both electronic and magnetic orders originating from competing electron populations on oxygen atoms. It shows an electric polarization of $50\mathrm{\mu }\mathrm{C}/{\mathrm{cm}}^2$, while the maximum linear and quadratic magnetoelectric response are as high as $35000\mathrm{ps}/\mathrm{m}$ and $1.59\times {10}^{-14}\mathrm{s}/\mathrm{A}$, respectively. Our Letter opens up new perspectives for the discovery and design of much-anticipated multiferroics that can be used for cross-modulation.

We show that long-wavelength interfacial fluctuations are strongly suppressed in nonequilibrium phase coexistence between bulk hyperuniform systems. Using simulations of three distinct microscopic models, we demonstrate that hyperuniform interfaces are much smoother than equilibrium ones, with a universal reduction of height fluctuations at large scale. We derive a nonequilibrium interface equation from the field theory of the bulk order parameter, and predict a reduction in height fluctuations, $S_h(\mathit{k})\equiv ⟨|h(\mathit{k}){|}^2⟩\sim |\mathit{k}{|}^{-1}$, in stark contrast to equilibrium capillary wave theory where $S_h(\mathit{k})\sim |\mathit{k}{|}^{-2}$. Our results establish a new universality class for nonequilibrium interfaces, highlighting the fundamental role of suppressed bulk fluctuations in shaping interfacial dynamics far from equilibrium.

When it comes to understanding how a cohesive object breaks up, there are two types of temptations: either seek detailed mechanisms (capillary instabilities for liquids, cracks, propagation in brittle solids...), or rely on a general principle to infer the multiplicity of the fragments’ sizes. Here we show that an original conservation law coupled with a maximal randomness principle provides new, unifying predictions. We explain when this principle is likely to apply, and why the fragment’s size distribution is a power law $p(d)\sim d^{-\beta }$, in that case, with exponent $\beta =D+1-\{{\pi }^{D/2}/[2^D(D/2)!]\},$ a function of the dimensionality of the breaking object $D$. Examples including crushed and grinned brittle materials like solid bars, plates, and shells; or cubes and spheroids; but also liquid drops and bubbles; exploding liquid shells; plastic debris in the ocean; and remnants from the cavemen industry are considered. The discussion is supplemented by an original experiment.