We report on the free decay of quasi-two-dimensional turbulence in superfluid ${}^4\mathrm{He}$ confined within nanofluidic channels. Using a pump-probe technique, we observe a complex decay of the vortex density $L(t)$ that deviates from a simple power law. The decay exhibits a universal fast transient, scaling as $L\propto t^{-2}$, followed by a slower nonuniversal regime that depends on the geometry and flow conditions. We demonstrate that this behavior is governed by the interplay between vortex pinning on the disordered topography of the channel walls and the mobilizing effect of the weak probe flow. A numerical model that treats pinning as a velocity-dependent effective mutual friction successfully reproduces the essential features of our experimental observations.

We report transport studies of hybrid Josephson junctions based on semiconducting InAs nanowires with fully overlapping epitaxial ferromagnetic insulator EuS and superconducting Al partial shells. Current-biased measurements reveal a hysteretic superconducting window with a sizable supercurrent near the coercive field of the ferromagnetic insulator, accompanied by multiple Andreev reflections. Tunneling spectroscopy shows a superconducting gap characterized by three peaks, which we attribute to tunneling between exchange-split superconductors. A theoretical model reproduces the observed features and indicates that spin mixing, driven by sizable spin-orbit coupling, is essential to their formation. Our results demonstrate proximity-induced superconductivity through a ferromagnetic insulator and establish a new platform for exploring spin-triplet pairing.

It seems self-evident that a density functional calculation should be normalized to the number of electrons in the system. We present multiple examples where the accuracy of the approximate energy is improved (sometimes greatly) by violating this basic principle. In one dimension, we explicitly derive the appropriate correction to the normalization. Beyond one dimension, Weyl asymptotics for energy levels yield these corrections for any cavity. We include examples with Coulomb potentials and the exchange energy of atoms to illustrate relevance to realistic calculations.

A thin-walled tubular superconductor develops a quantized fluxoid in the presence of an axial magnetic field. The fluxoid corresponds to the number of phase windings of the superconducting order parameter and is topological in nature. When the tube has a radius variation along the axial direction, forming a bottleneck structure between sections with different radius, a fluxoid mismatch can appear depending on the applied magnetic field. The bottleneck then becomes a topological boundary and is host to topologically protected solutions for the order parameter, dubbed fluxoid solitons, that are free to move around bottlenecks with cylindrical symmetry. Fluxoid solitons are a new type of vortex with nonquantized flux, loosely related to Pearl vortices in thin superconducting films, and fluxons in Corbino Josephson junctions. We characterize their properties as a function of system parameters using the self-consistent quasiclassical theory of diffusive superconductors. We consider both short bottleneck structures and long tapered tubes, where multiple trapped fluxoid solitons adopt elaborate arrangements dictated by their mutual repulsion.

In ordinary solids, nonlinear optical responses are typically studied in terms of unit-cell averages due to the ångström-scale lattice constants. In contrast, moiré superlattices, characterized by a large length scale, unlock an often-overlooked degree of freedom: intrasupercell spatial variations of local observables. Here, we formulate the second-order direct current (dc) charge response in a spatially resolved manner, showing that even uniform optical illumination can drive a static, spatially nonuniform charge redistribution within a supercell. This effect is ubiquitous and cannot be forbidden by any crystalline symmetries. Furthermore, we identify a dominant contribution arising from diverging analytical response coefficients, which leads to linear-in-time growth of the redistribution in the absence of relaxation. This growth is driven by the convergence or divergence of local dc photocurrents. Applying our theory to twisted bilayer ${\mathrm{MoTe}}_2$, we demonstrate strong, highly tunable charge modulation controlled by light intensity and frequency, opening a route to in situ, all-optical control of moiré-periodic electrostatic potentials. Our Letter underscores the importance of intracell degrees of freedom, which enable a qualitatively richer class of nonlinear optical responses in moiré superlattices.

Motility-induced phase separation (MIPS) is a distinctive phenomenon in active matter that arises from its inherent nonequilibrium nature. Despite recent progress in understanding MIPS in dry active systems, it has been debated whether MIPS can be observed in wet systems in which fluid-mediated hydrodynamic interactions (HIs) are present. We use theory and large-scale active fast Stokesian dynamics simulations of the so-called squirmer model to show that collision-induced pusher force dipoles, which are present even for the simplest neutral squirmers (stealth swimmers), destroy MIPS when HIs are included. Both rotational and translational HIs independently suppress phase separation: rotation by shortening a swimmer’s persistence length (and thus reducing the swim pressure), and translation by a confinement-scale advective fluid flow. We further clarify that collisional dipoles between swimmers and boundaries can generate attractive flows that promote particle aggregation observed in some previous simulations and experiments. Finally, we show how to recover MIPS in fluidic environments by tuning the magnitude of the HIs through brushlike surface coatings on the active particles.

Hydrogen-rich lanthanum compounds show the highest known superconducting transition temperatures at high pressure. Despite the pivotal role of hydrogen within these systems, there has been no systematic exploration of how the composition and superconducting properties are intertwined. Our experimental and computational studies demonstrate that A15-type ${\mathrm{LaH}}_{5.75-x}$ hosts high-$T_c$ superconductivity ($T_c=98\mathrm{K}$ at 94 GPa) when available interstitial sites are fully occupied with hydrogen. Upon decompression, a site-selective hydrogen depopulation drives a superconductor-to-insulator transition with a threshold composition of ${\mathrm{LaH}}_5$. Strikingly, the A15 framework is experimentally retained from 120 to 4 GPa, with reversible pressure-dependent hydrogen content changes from ${\mathrm{LaH}}_{5.75}$ down to ${\mathrm{LaH}}_{3.25}$. Our results demonstrate the exceptional stability and tunability of the A15 framework, offering a unique platform to probe the interplay between composition, structure, and superconductivity in hydrogen-rich materials.

We report electric field-controlled modulation of the Fermi surface topology and explore its effects on the superconducting state in alternating-angle twisted quadrilayer graphene (TQG). The unique combination of flat and dispersive bands in TQG allows us to simultaneously tune the band structure through carrier density, $n$, and displacement field, $D$. From density-dependent Shubnikov–de Haas quantum oscillations and Hall measurements, we quantify the $D$-dependent bandwidth of the flat and dispersive bands and their hybridization. In the high $|D|$ regime, the increased bandwidth favors the single particle bands, which coincides exactly with the vanishing of the superconducting transition temperature $T_c$, showing that superconductivity in TQG is strongly bound to the symmetry-broken state. For a range of lower $|D|$ values, a Lifshitz transition occurs when the flat and dispersive band Fermi surfaces merge within the $\nu =+2$ symmetry-broken state. The superconducting state correspondingly shows an enhanced $T_c$, suggesting that the superconducting condensate is strongly dependent on the Fermi surface topology and density of states within this symmetry-broken state.

High-order anisotropic magnetoresistance (AMR) is observed up to the 18th harmonic in cubic Fe(001) thin films, overturning the long-standing paradigm that only two-fold and four-fold terms are symmetry-allowed. Using angle-resolved transport and Fourier analysis, we show that six-fold and higher-order terms are intrinsic, tunable by temperature and thickness, and predicted by crystal symmetry. Microscopically, the two-fold sign reversal arises from a crossover between weak and strong scattering regimes, while high-order terms emerge from the interplay of anisotropic Fermi velocity and relaxation time. Our results establish high-order AMR as a symmetry-prescribed property of cubic ferromagnets, providing critical benchmarks for spin-orbit transport theory and enabling new angular-sensitive spintronic functionalities.

We study clogging of cohesive particles in a two-dimensional hopper with experiments and simulations. The system consists of buoyant, monodisperse oil droplets in an aqueous solution, where the droplet size, buoyant force, cohesion, and hopper opening are varied. Stronger cohesion enhances clogging, a trend confirmed in simulations. Balancing buoyant and cohesive forces defines a cohesive length scale that collapses the data onto a master curve. Thus, under strong cohesion, we find that clogging is governed not by particle diameter, but by the cohesive length scale.

Many swimming microorganisms navigate their environment by modulating the curvature of their swimming trajectories in response to external cues. Here, we show that the biflagellate alga Chlamydomonas reinhardtii swims in circles and actively switches its trajectory handedness in response to orthogonal illumination: the cell swims counterclockwise at low light intensities yet clockwise at high light intensities. This handedness switching arises from light-dependent modulation of flagellar beating, including rapid and reversible changes in beat extension, phase, and—crucially—beat plane orientation. Using high-speed imaging and hydrodynamic modeling, we reveal that this beat plane reorientation is critical for Chlamydomonas to swim orthogonally to light as well as to dynamically modulate its trajectory curvature, enabling transitions between global exploration and localized searching in spatially structured light fields. Our results establish beat plane reorientation as a novel mechanism for curvature control in microswimmer navigation.

A power ramp from L- to H-mode-like conditions is carried out in a 50 ms long global full-$f$ turbulence simulation of ASDEX Upgrade with the grillix code. After 32 ms of slow profile evolution, a sudden change in transport triggers a pedestal buildup within $\sim 100\mathrm{\mu }\mathrm{s}$. This transition results from an abrupt shift from drift-wave (DW) to kinetic-ballooning-mode (KBM) turbulence. The self-consistently evolved $E\times B$ flow shear first increases slowly and then sharply. Geodesic acoustic mode and Alfvénic flow oscillations intensify prior to the transition and subsequently die out. This is followed by slow oscillations of the transport and profiles, reminiscent of a dithering I-phase or edge-localized-mode (ELM) cycles observed experimentally. This study paves the way for a better understanding of confinement regime transitions.

We report ultrahigh magnetic field Faraday rotation results on the chiral helimagnet ${\mathrm{Cu}}_2{\mathrm{OSeO}}_3$, the first Mott insulator showing skyrmion lattice phases and a linear magnetoelectric effect. Between 180 and 300 T, we find signatures of a Bose-Einstein condensation of magnons, which can be described as a canted XY ferrimagnet. Because of the magnetoelectric coupling, the transverse magnetic order of the individual ${\mathrm{Cu}}^{2+}$ spins is accompanied by a characteristic domelike electric polarization which is crucial for the observation of the condensate via the Faraday rotation effect.

Gravitational waves emitted in the late inspiral of binary neutron stars are affected by their tidal deformation. We study the tidal dynamics in full general relativity through matched-asymptotic expansions and show that the dynamical tidal response can be expanded in a set of modes. We further show that the mode amplitudes satisfy an effective, forced harmonic oscillator equation, which generalizes the overlap-integral formulation of Newtonian gravity. Our relativistic treatment of dynamical tides will avoid systematic biases in future gravitational-wave parameter estimation and can be generalized to model nonlinear tidal interactions and include the presence of elastic, electromagnetic, or dark matter field interactions with nuclear matter.

We report a search for exotic spin-spin interactions between neutrons and electrons which could signal new physics beyond the standard model using slow neutron polarimetric imaging through a dense medium of polarized electrons. Our dense polarized electron target is a ferrimagnet held at its magnetic compensation temperature, which realizes a polarized electron ensemble with zero net magnetization. We sought the spin rotation of transversely polarized neutrons from a neutron-spin–electron-spin interaction of the form $V_2=-g_A^e{g}_A^n(\hslash c/4\pi ){\overrightarrow{\sigma }}_e·{\overrightarrow{\sigma }}_n(e^{-r/{\lambda }_c}/r)$, where $g_A^e$ and $g_A^n$ are the electron and neutron axial couplings, $\overrightarrow{{\sigma }_e}$ and $\overrightarrow{{\sigma }_n}$ are the electron and neutron spin, and ${\lambda }_c$ is the interaction range for an exotic axial vector interaction from massive spin-1 boson exchange of mass $\hslash c/{\lambda }_c$. The resulting average neutron-spin-rotation angle per unit length, $(d{\overline{\varphi }}_{F5}/dz)=[0.41\pm 6.3(\mathrm{stat})\pm 4.4(\mathrm{sys})]\times {10}^{-3}\mathrm{rad}/\mathrm{m}$, is consistent with zero. Our novel approach improves the previous upper limits on the coupling constant product $g_A^e{g}_A^n$ by several orders of magnitude in the poorly explored ${10}^{-8}\le {\lambda }_c\le {10}^{-2}\mathrm{m}$ range.

Polarized single-photon sources (SPSs) are valuable for quantum information applications and can be implemented by exploiting an elliptical or birefringent cavity that provide polarization-selective Purcell enhancement. However, current designs suffer from similar quality ($Q$) factors of split cavity modes, requiring both high Purcell factor and substantial mode splitting for ideal polarization performance. Here, we report a low-Purcell anisotropic Dirac cavity that supports orthogonally polarized modes with significantly distinct $Q$ factors (1032 vs 98). When coupled to a single quantum dot, this cavity enables single-photon emission [$g^{(2)}(0)=0.028$] with $>99\%$ degree of linear polarization (DoLP). The high DoLP is tolerant to emission wavelength, originating from suppression of competing radiative channels. Lifetime measurements demonstrate a 1.72-fold enhancement at cavity resonance and a 3.47-fold inhibition in a photonic band gap. Additionally, the anisotropic Dirac cavity exhibits vertical directionality with simulated collection efficiency up to 92.7%. Our results offer a novel strategy toward ideal solid-state polarized SPSs.

Achieving high-fidelity qubit readout and reset while maintaining qubit coherence is crucial for quantum error correction and advanced quantum algorithms. Here, we design and experimentally demonstrate a scalable architecture based on frequency-tunable nonlinear Purcell filters, which enables flexible readout and rapid unconditional reset of multiple superconducting qubits. Our readout protocol dynamically adjusts the effective linewidth of the readout resonator through a tunable Purcell filter, optimizing the signal-to-noise ratio during measurement while suppressing photon noise during idle periods. Combined with a multilevel readout protocol, we achieve the highest readout fidelity of 99.3% without any quantum-limited amplifier, even with a small dispersive shift. Moreover, by leveraging a reset channel formed via the adjacent coupling between the filter and the coupler, we realize unconditional qubit reset of both leakage-induced $|2⟩$ and $|1⟩$ states within 200 ns and reset of the $|1⟩$ state alone within 75 ns, with error rates $\le 1\%$. The filter also mitigates both photon-induced dephasing and the Purcell effect, thereby preserving qubit coherence. This scalable Purcell filter architecture shows exceptional performance in qubit readout, reset, and protection, marking it as a promising hardware component for advancing fault-tolerant quantum computing systems.

Entangled states hold the promise of improving the precision and accuracy of quantum sensors. We experimentally demonstrate that spectroscopy of an optical clock transition using entangled states can outperform its classical counterpart. Two ${{}^{40}\mathrm{Ca}}^{+}$ ions are entangled in a quantum state with vanishing first-order magnetic field sensitivity, extending the coherence time of the atoms and enabling near-lifetime-limited probe times of up to 550 ms. In our protocol, entangled ions reach the same instability as uncorrelated ions, but at half the probe time, enabling faster cycle times of the clock. We run two entangled ${{}^{40}\mathrm{Ca}}^{+}$ ions as an optical clock and compare its frequency instability with a ${}^{87}\mathrm{Sr}$ lattice clock. The instability of the entangled ion clock is below a clock operated with classically correlated states for all probe times. We observe instabilities below the theoretically expected quantum projection noise limit of two uncorrelated ions for interrogation times below 100 ms. The lowest fractional frequency instability of $7\times {10}^{-16}/\sqrt{\tau /1\mathrm{s}}$ is reached for 250 ms probe time, limited by residual phase noise of the probe laser. This represents the lowest instability reported to date for a ${{}^{40}\mathrm{Ca}}^{+}$ ion clock.

Structural superlubricity (SSL) promises nearly frictionless and wearless sliding but has until now been considered a special and extreme interfacial phenomenon limited to micro- and nanoscale contacts. Here, we demonstrate robust macroscale SSL within a single submillimeter graphite contact. Previously reported near-zero friction coefficients, where friction is nearly independent of normal load, have only been observed at microscale contacts under low loads. Our system expands both contact size and load into the macroscopic regime, exhibiting friction coefficients that fluctuate around zero and reach values as low as $\sim {10}^{-6}$ across a broad load range from 1 mN to 0.5 N. Negative friction coefficients are also observed. Similar behavior is observed at graphite$/{\mathrm{MoS}}_2$ interfaces, indicating that macroscale SSL is a generalizable phenomenon across flat layered materials. These findings overturn long-standing scaling limitations and establish macroscale SSL as a paradigm-shifting platform for next-generation mechanical and electromechanical systems.

Monolayers (MLs) of semiconducting transition metal dichalcogenides emit light very efficiently and display rich spin-valley physics, with gyromagnetic ($g$) factors of about $-4$. Here, we investigate how these properties can be tailored by alloying. Magneto-optical spectroscopy is used to reveal the peculiar properties of excitonic complexes in ${\mathrm{Mo}}_x{\mathrm{W}}_{1-x}{\mathrm{Se}}_2$ MLs with different metal concentrations. We show that the alloys feature extremely high $g$ factors for neutral excitons, that change gradually with the composition up to reaching values of the order of $-10$ for $x\approx 0.2$. First-principles calculations quantitatively identify the alloy-induced mixing between different conduction band valleys as the underlying mechanism originating the anomalous composition dependence of the neutral exciton $g$ factor. The theoretical framework also suggests a high strain sensitivity of the alloys, making them promising candidates for tailor-made optoelectronic devices.