We have produced persistent currents of ultracold fermionic atoms trapped in a ring, with lifetimes greater than 10 sec in the strongly interacting regime. These currents remain stable well into the BCS regime at sufficiently low temperature. We drive a circulating BCS superfluid into the normal phase and back by changing the interaction strength and find that the probability for quantized superflow to reappear is remarkably insensitive to the time spent in the normal phase and the minimum interaction strength. After ruling out spontaneous current formation for our experimental conditions, we argue that the reappearance of superflow is due to weak damping of normal currents in this limit. These results establish that ultracold fermionic atoms with tunable interactions can be used to create matter-wave circuits similar to those previously created with weakly interacting bosonic atoms.

A unique feature of non-Hermitian (NH) systems is the NH skin effect, i.e., the edge localization of an extensive number of bulk-band eigenstates in a lattice with open or semi-infinite boundaries. Unlike extended Bloch waves in Hermitian systems, the skin modes are normalizable eigenstates of the Hamiltonian that originate from the intrinsic non-Hermitian point-gap topology of the Bloch band energy spectra. Here, we unravel a fascinating property of NH skin modes, namely self-healing, i.e., the ability to self-reconstruct their shape after being scattered off by a space-time potential.

Zwitterionic modification of colloids with weak acids and bases represents a promising strategy in creating functional materials with tunable properties and modeling the self-organization of charged proteins. However, accurate incorporation of the dynamic dissociation or association of ionization groups known as charge regulation (CR) is often intractable in theoretical and computational investigations since charge redistribution and configuration need to be evolved self-consistently. Using hybrid Monte Carlo and molecular dynamics simulations, we demonstrate that a dilute suspension of overall charge-neutral zwitterionic Janus nanoparticles shows a conformational transition from an open assembly of string or bundle to compact cluster along with the variation in $p\mathrm{H}$. The behavior under CR is qualitatively different from the commonly employed constant charge condition where the transition is absent. The CR-induced clustering is due to the inhomogeneous and fluctuating charges localized near the equatorial boundary of the Janus particle. These features are enhanced particularly at low salt concentration and high electrostatic coupling strength. Our results indicate the critical role of charge regulation in the spatial self-organization of zwitterionic nanoparticles.

We report precision determinations of the beam-normal single spin asymmetries ($A_n$) in the elastic scattering of 0.95 and 2.18 GeV electrons off ${}^{12}\mathrm{C}$, ${}^{40}\mathrm{Ca}$, ${}^{48}\mathrm{Ca}$, and ${}^{208}\mathrm{Pb}$ at very forward angles where the most detailed theoretical calculations have been performed. The first measurements of $A_n$ for ${}^{40}\mathrm{Ca}$ and ${}^{48}\mathrm{Ca}$ are found to be similar to that of ${}^{12}\mathrm{C}$, consistent with expectations and thus demonstrating the validity of theoretical calculations for nuclei with $\mathrm{Z}\le 20$. We also report $A_n$ for ${}^{208}\mathrm{Pb}$ at two new momentum transfers (${\mathrm{Q}}^2$) extending the previous measurement. Our new data confirm the surprising result previously reported, with all three data points showing significant disagreement with the results from the $Z\le 20$ nuclei. These data confirm our basic understanding of the underlying dynamics that govern $A_n$ for nuclei containing $\lesssim 50$ nucleons, but point to the need for further investigation to understand the unusual $A_n$ behavior discovered for scattering off ${}^{208}\mathrm{Pb}$.

A many-mode laser with nonlinear modal interaction could serve as a model system to study many-body physics. However, precise and continuous tuning of the interaction strength over a wide range is challenging. Here, we present a unique method for controlling lasing mode structures by introducing random phase fluctuation to a nearly degenerate cavity. We show numerically and experimentally that as the characteristic scale of phase fluctuation decreases by two orders of magnitude, the transverse modes become fragmented and the reduction of their spatial overlap suppresses modal competition for gain, allowing more modes to lase. The tunability, flexibility, and robustness of our system provides a powerful platform for investigating many-body phenomena.

The energies of valley-orbit states in silicon quantum dots are determined by an as yet poorly understood interplay between interface roughness, orbital confinement, and electron interactions. Here, we report measurements of one- and two-electron valley-orbit state energies as the dot potential is modified by changing gate voltages, and we calculate these same energies using full configuration interaction calculations. The results enable an understanding of the interplay between the physical contributions and enable a new probe of the quantum well interface.

We study a non-Markovian and nonstationary model of animal mobility incorporating both exploration and memory in the form of preferential returns. Exact results for the probability of visiting a given number of sites are derived and a practical WKB approximation to treat the nonstationary problem is developed. A mean-field version of this model, first suggested by Song et al., [Modelling the scaling properties of human mobility, Nat. Phys. 6, 818 (2010)] was shown to well describe human movement data. We show that our generalized model adequately describes empirical movement data of Egyptian fruit bats (Rousettus aegyptiacus) when accounting for interindividual variation in the population. We also study the probability of visiting any site a given number of times and derive a mean-field equation. Our analysis yields a remarkable phase transition occurring at preferential returns which scale linearly with past visits. Following empirical evidence, we suggest that this phase transition reflects a trade-off between extensive and intensive foraging modes.

Quantum batteries are devices made from quantum states, which store and release energy in a fast and efficient manner, thus offering numerous possibilities in future technological applications. They offer a significant charging speedup when compared to classical batteries, due to the possibility of using entangling charging operations. We show that the maximal speedup that can be achieved is extensive in the number of cells, thus offering at most quadratic scaling in the charging power over the classically achievable linear scaling. To reach such a scaling, a global charging protocol, charging all the cells collectively, needs to be employed. This concludes the quest on the limits of charging power of quantum batteries and adds to other results in which quantum methods are known to provide at most quadratic scaling over their classical counterparts.

We report the first observation of intermolecular Coulombic decay (ICD) in liquid water following inner-valence ionization. By combining a monochromatized tabletop high-harmonic source with a liquid microjet, we record electron-electron coincidence spectra at two photon energies that identify the ICD electrons, together with the photoelectrons originating from the $2a_1$ inner-valence band of liquid water. Our results confirm the importance of ICD as a source of low-energy electrons in bulk liquid water and provide quantitative results for modeling the velocity distribution of the slow electrons that are thought to dominate radiation damage in aqueous environments.

We explore the physical origin and the general validity of a propensity rule for the conservation of the hyperfine spin state in three-body recombination. This rule was recently discovered for the special case of ${}^{87}\mathrm{Rb}$ with its nearly equal singlet and triplet scattering lengths. Here, we test the propensity rule for ${}^{85}\mathrm{Rb}$ for which the scattering properties are very different from ${}^{87}\mathrm{Rb}$. The ${\mathrm{Rb}}_2$ molecular product distribution is mapped out in a state-to-state fashion using resonance-enhanced multiphoton ionization detection schemes which fully cover all possible molecular spin states. Interestingly, for the experimentally investigated range of binding energies from zero to $\sim 13\mathrm{GHz}\times h$ we observe that the spin-conservation propensity rule also holds for ${}^{85}\mathrm{Rb}$. From these observations and a theoretical analysis we derive an understanding for the conservation of the hyperfine spin state. We identify several criteria to judge whether the propensity rule will also hold for other elements and collision channels.

We study turbulent Rayleigh-Bénard convection over four decades of Rayleigh numbers $4\times {10}^8<\mathrm{Ra}<2\times {10}^{12}$, while harmonically modulating the temperatures of the plates of our cylindrical cell. We probe the flow by temperature sensors placed in the cell interior and embedded in the highly conducting copper plates and detect thermal waves propagating at modulation frequency in the bulk of the convective flow. We confirm the recent numerical prediction [Yang et al., Phys. Rev. Lett. 125, 154502 (2020)] of the significant enhancement of the Nusselt number and report its dependence on the frequency and amplitude of the temperature modulation of plates.

Spin-orbit coupling (SOC) is a key to understand the magnetically driven superconductivity in iron-based superconductors, where both local and itinerant electrons are present and the orbital angular momentum is not completely quenched. Here, we report a neutron scattering study on the bilayer compound $\mathrm{CaK}{({\mathrm{Fe}}_{0.96}{\mathrm{Ni}}_{0.04})}_4{\mathrm{As}}_4$ with superconductivity coexisting with a noncollinear spin-vortex crystal magnetic order that preserves the tetragonal symmetry of the Fe-Fe plane. In the superconducting state, two spin resonance modes with odd and even $L$ symmetries due to the bilayer coupling are found similar to the undoped compound ${\mathrm{CaKFe}}_4{\mathrm{As}}_4$ but at lower energies. Polarization analysis reveals that the odd mode is $c$-axis polarized, and the low-energy spin anisotropy can persist to the paramagnetic phase at high temperature, which closely resembles other systems with in-plane collinear and $c$-axis biaxial magnetic orders. These results provide the missing piece of the puzzle on the SOC effect in iron-pnictide superconductors, and also establish a common picture of $c$-axis preferred magnetic excitations below $T_c$ regardless of the details of magnetic pattern or lattice symmetry.

We employ analytical and numerical approaches to show that unpaired Majorana zero modes can occur in cores of Abrikosov vortices at the interface between a three-dimensional topological insulator, such as ${\mathrm{Bi}}_2{\mathrm{Se}}_3$, and a twisted bilayer of high-$T_c$ cuprate superconductor, such as ${\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_{8+\delta }$. When the twist angle is close to 45° the latter has been predicted to form a fully gapped topological superconductor up to temperatures approaching its native $T_c\simeq 90\mathrm{K}$. Majorana zero modes in these structures will persist up to unprecedented high temperatures and, depending on the quality of the interface, may be protected by gaps with larger magnitudes than other candidate systems.

We introduce the Broadband Reflector Experiment for Axion Detection (BREAD) conceptual design and science program. This haloscope plans to search for bosonic dark matter across the $[{10}^{-3},1]\mathrm{eV}$ ([0.24, 240] THz) mass range. BREAD proposes a cylindrical metal barrel to convert dark matter into photons, which a novel parabolic reflector design focuses onto a photosensor. This unique geometry enables enclosure in standard cryostats and high-field solenoids, overcoming limitations of current dish antennas. A pilot $0.7{\mathrm{m}}^2$ barrel experiment planned at Fermilab is projected to surpass existing dark photon coupling constraints by over a decade with one-day runtime. Axion sensitivity requires $<{10}^{-20}\mathrm{W}/\sqrt{\mathrm{Hz}}$ sensor noise equivalent power with a 10 T solenoid and $10{\mathrm{m}}^2$ barrel. We project BREAD sensitivity for various sensor technologies and discuss future prospects.

We demonstrate enhanced Andreev reflection in a $\mathrm{Nb}/\mathrm{InGaAs}/\mathrm{InP}$-based superconductor-semiconductor hybrid device resulting in increased Cooper-pair injection efficiency, achieved by Cooper-pair tunneling into a semiconductor quantum well resonant state. We show this enhancement by investigating the differential conductance spectra of two kinds of samples: one exhibiting resonant states and one which does not. We observe resonant features alongside strong enhancement of Cooper pair injection in the resonant sample, and lack of Cooper pair injection in the nonresonant sample. The theoretical modeling for measured spectra by a numerical approach agrees well with the experimental data. Our findings open a wide range of directions in condensed matter physics and in quantum technologies such as superconducting light-emitting diodes and structures supporting exotic excitations.

We study the quantum gravitational collapse of spherically symmetric pressureless dust. Using an effective equation derived from a polymer quantization in the connection-triad phase space variables of general relativity, we find numerically, for a variety of initial dust configurations, that (i) trapped surfaces form and disappear as an initially collapsing density profile evolves into an outgoing shock wave; (ii) black hole lifetime is proportional to the square of its mass; and (iii) there is no mass inflation at inner apparent horizons. These results provide a substantially different view of black hole formation and subsequent evolution than found from semiclassical analyses.

Recent transport studies have demonstrated the great potential of twisted monolayer-bilayer graphene (TMBG) as a new platform to host moiré flat bands with a higher tunability than twisted bilayer graphene (TBG). However, a direct visualization of the flat bands in TMBG and its comparison with the ones in TBG remain unexplored. Here, via fabricating on a single sample with exactly the same twist angle of $\sim 1.13°$, we present a direct comparative study between TMBG and TBG using scanning tunneling microscopy and spectroscopy. We observe a sharp density of states peak near the Fermi energy in tunneling spectroscopy, confirming unambiguously the existence of flat electronic bands in TMBG. The bandwidth of this flat-band peak is found to be slightly narrower than that of the TBG, validating previous theoretical predictions. Remarkably, by measuring spatially resolved spectroscopy, combined with continuum model calculation, we show that the flat-band states in TMBG exhibit a unique layer-resolved localization-delocalization coexisting feature, which offers an unprecedented possibility to utilize their cooperation on exploring novel correlation phenomena. Our work provides important microscopic insight of flat-band states for better understanding the emergent physics in graphene moiré systems.

We present a theory of evolution of wind waves in time and space under abruptly applied wind forcing that is experimentally validated in a laboratory wind-wave tank. The model describes qualitatively and quantitatively the complex wave field development from the initial smooth surface to the finite state. The stochastic nature of wind waves is treated by considering an ensemble of coexisting unstable harmonics that grow due to shear flow instability. Breaking limits the wave growth initially; the process is then controlled by fetch-limited growth duration.

The properties of photoemission electron sources determine the ultimate performance of a wide class of electron accelerators and photon detectors. To date, all high-efficiency visible-light photocathode materials are either polycrystalline or exhibit intrinsic surface disorder, both of which limit emitted electron beam brightness. In this Letter, we demonstrate the synthesis of epitaxial thin films of ${\mathrm{Cs}}_3\mathrm{Sb}$ on 3C-SiC (001) using molecular-beam epitaxy. Films as thin as 4 nm have quantum efficiencies exceeding 2% at 532 nm. We also find that epitaxial films have an order of magnitude larger quantum efficiency at 650 nm than comparable polycrystalline films on Si. Additionally, these films permit angle-resolved photoemission spectroscopy measurements of the electronic structure, which are found to be in good agreement with theory. Epitaxial films open the door to dramatic brightness enhancements via increased efficiency near threshold, reduced surface disorder, and the possibility of engineering new photoemission functionality at the level of single atomic layers.

Nanodiamonds with embedded nitrogen-vacancy (NV) centers have emerged as promising magnetic field sensors, as hyperpolarizing agents in biological environments, as well as efficient tools for spin mechanics with levitating particles. These applications currently suffer from random environmental interactions with the diamond which implies poor control of the N-V direction. Here, we predict and report on a strong diamagnetism of a pure spin origin mediated by a population inversion close to a level crossing in the NV center electronic ground state. We show control of the sign of the magnetic susceptibility as well as angle locking of the crystalline axis of a microdiamond along an external magnetic field, with bright perspectives for these applications.