Chiral interactions within magnetic layers stabilize the formation of noncollinear spin textures, which can be leveraged to design devices with tailored magnetization dynamics. Here, we introduce chiral spin frustration in which energetically degenerate magnetic states frustrate the Dzyaloshinskii-Moriya interaction. We demonstrate magnon-driven switching of the chirally frustrated spin states in Bi-substituted yttrium iron garnet thin films. These states are defined by an in-plane macrospin neighboring two out-of-plane spins on either side with opposing chirality. Using scanning nitrogen-vacancy magnetometry and spin pumping, we identified four degenerate frustrated states and achieved their controllable switching via magnon spin torque. Crucially, the switching is unidirectional, with selectivity determined by the incoming magnon direction. This mechanism provides a powerful approach to manipulate frustrated spin states with magnons. Chiral spin frustration unlocks the geometry constraints of conventional frustration, and therefore opens new horizons for frustrated magnetism, paving the way for energy-efficient spintronic devices based on frustration.

Measurements of the EMC effect in the tritium and helium-3 mirror nuclei are reported. The data were obtained by the MARATHON Jefferson Lab experiment, which performed deep inelastic electron scattering from deuterium and the three-body nuclei, using a cryogenic gas target system and the high resolution spectrometers of the Hall A Facility of the Lab. The data cover the Bjorken $x$ range from 0.20 to 0.83, corresponding to a squared four-momentum transfer $Q^2$ range from 2.7 to $11.9(\mathrm{GeV}/c{)}^2$, and to an invariant mass $W$ of the final hadronic state greater than $1.84\mathrm{GeV}/c^2$. The tritium EMC effect measurement is the first of its kind. The MARATHON experimental results are compared to results from previous measurements by DESY-HERMES and JLab–Hall C experiments, as well as with few-body theoretical predictions.

The inelastic neutron scattering results and their analysis unequivocally point to a dominant Kitaev interaction in the honeycomb-lattice cobaltate ${\mathrm{BaCo}}_2({\mathrm{AsO}}_4{)}_2$. Our anisotropic-exchange model closely describes all available neutron scattering data in the material’s field-polarized phase. The density-matrix renormalization group results for our model are in close accord with the unusual double-zigzag magnetic order and the low in-plane saturation field of ${\mathrm{BaCo}}_2({\mathrm{AsO}}_4{)}_2$.

While ballistic electrons are a key tool for applications in sensing and flying qubits, sub-nanosecond propagation times and complicated interactions make control of ballistic single electrons challenging. Recent experiments have revealed Coulomb collisions of counterpropagating electrons in a beam splitter, giving time resolved control of interactions between single electrons. Here we use remote Coulomb interactions to demonstrate a scheme for sensing single ballistic electrons. We show that interactions are highly controllable via electron energy and emission timing. We use a weakly coupled “sensing” regime to characterize the nanoscale potential landscape of the beam splitter and the strength of the Coulomb interaction. We also show multielectron sensing with picosecond resolution.

Time-varying media break temporal translation symmetry, enabling advanced wave manipulation. However, this phenomenon remains largely unexplored in magnonic systems due to the challenge of achieving rapid and significant changes in magnon dispersion. Here, we construct a time-varying strong coupling between two magnon modes and observe chirped Rabi-like oscillations near the pulse edges. Developing a time-resolved frequency-comb spectroscopy technique, we characterize the frequency conversion of magnon modes induced by the time-varying strong-coupling effect. Moreover, we construct time slits with adjacent time interfaces and, for the first time, demonstrate the double-slit time diffraction of magnon modes, analogous to the well-known Young’s double-slit experiment. These findings rely solely on the time-varying strong coupling, independent of device reconfiguration. Our results open avenues for applications such as all-magnetic mixers or on-chip gigahertz sources.

We use the thermal effective theory to prove that, for the vacuum state in any conformal field theory in $d$ dimensions, the $n$th Rényi entropy $S_A^{(n)}$ behaves as $S_A^{(n)}=[f/(2\pi n{)}^{d-1}][\text{Area}(\partial A)/(d-2){\epsilon }^{d-2}](1+O(n))$ in the $n\to 0$ limit when the boundary of the entanglement domain $A$ is spherical with the UV cutoff $\epsilon$. The theory dependence is encapsulated in the cosmological constant $f$ in the thermal effective action. Using this result, we estimate the density of states for large eigenvalues of the modular Hamiltonian for the domain $A$. In two dimensions, we can use the hot spot idea, which describes the effective action in the high-temperature limit when the temperature is position-dependent, to derive more powerful formulas valid for arbitrary positive $n$. We discuss the difference between two and higher dimensions and clarify the applicability of the hot spot idea. We also use the thermal effective theory to derive an analog of the Cardy formula for boundary operators in higher dimensions.

Controlling the Stark perturbation from ambient thermal radiation is key to advancing the performance of many atomic frequency standards, including state-of-the-art optical lattice clocks (OLCs). We demonstrate a cryogenic OLC that utilizes a dynamically actuated radiation shield to control the perturbation at $1.7\times {10}^{-20}$ fractional frequency, a factor of $\sim 40$ beyond the best OLC to date. Our shield furnishes the atoms with a near-ideal cryogenic blackbody radiation (BBR) environment by rejecting external thermal radiation at the part-per-million level during clock spectroscopy, overcoming a key limitation with previous cryogenic BBR control solutions in OLCs. While the lowest BBR shift uncertainty is realized with cryogenic operation, we further exploit the radiation control that the shield offers over a wide range of temperatures to directly measure and verify the leading BBR Stark dynamic correction coefficient for ytterbium. This independent measurement reduces the literature-combined uncertainty of this coefficient by 30%, thus benefiting state-of-the-art Yb OLCs operated at room temperature. We verify the static BBR coefficient for Yb at the low ${10}^{-18}$ level.

We study particle acceleration in strongly turbulent pair plasmas using novel 3D particle-in-cell simulations, featuring particle injection from an external heat bath and diffusive escape. We demonstrate the formation of steady-state, nonthermal particle distributions with maximum energies reaching the Hillas limit. The steady state is characterized by the equilibration of plasma kinetic and magnetic pressures, which imposes upper limits on the acceleration rate. With growing cold plasma magnetization ${\sigma }_0$, nonthermal power-law spectra become harder, and the fraction of energy channeled into escaping cosmic rays increases. At ${\sigma }_0\gtrsim 1$, the escaping cosmic rays amount to more than 50% of the dissipated energy. Our method allows for kinetic studies of particle acceleration under steady-state conditions, with applications to a variety of astrophysical systems.

We present a conceptually simple and technically straightforward method for calculating photoelectron wave functions that is easily integrable with standard wave-function-based density-functional-theory packages. Our method is based on the Lippmann-Schwinger equation, naturally incorporating the boundary condition that the final photoelectron state must satisfy. The calculated results are in good agreement with the measured photon-energy and polarization dependence of the angle-resolved photoemission spectroscopy (ARPES) of graphene, the photon-energy-dependent evolution of the so-called dark corridor arising from the pseudospin, and ${\mathrm{WSe}}_2$, the circular dichroism reflecting the hidden orbital polarization. Our Letter opens doors to do-it-yourself simulations of ARPES with standard density-functional-theory packages, of crucial importance in the era of “quantum materials,” whose key experimental tool is ARPES.

Quantum information scrambling, which describes the propagation and effective loss of local information, is crucial for understanding the dynamics of quantum many-body systems. We report the observation of anomalous information scrambling in an atomic tweezer array with dominant van der Waals interaction. We characterize information spreading by an out-of-time-order correlator and observe persistent oscillations inside a suppressed linear light cone for the initial Néel state. Such an anomalous dynamic, which differs from both generic thermal and many-body localized scenarios, originates from weak ergodicity breaking in quantum many-body scarred systems.

Direct-detection searches for dark matter are insensitive to dark matter particles that have large interactions with ordinary matter, which are stopped in the atmosphere or the Earth’s crust before reaching terrestrial detectors. We use “dark” calibration images taken with the HgCdTe detectors in the near-infrared spectrograph (NIRSpec) on the James Webb Space Telescope (JWST) to derive novel constraints on sub-GeV dark matter candidates that scatter off electrons. We supplement the JWST analysis pipeline with additional masks to remove pixels with high-energy background events. For a 0.4% subcomponent of dark matter that interacts with an ultralight dark photon, we disfavor all previously allowed parameter space at high cross sections, and constrain some parameter regions for subcomponent fractions as low as $\sim 0.01\%$.

In semiconducting-superconducting hybrid devices, Andreev bound states (ABSs) can mediate the coupling between quantum dots, allowing for the realization of artificial Kitaev chains. In order to engineer Majorana bound states (MBSs) in these systems, one must control the energy of the ABSs. In this Letter, we show how extended ABSs in a flux-tunable Josephson junction can be used to control the coupling between distant quantum dots separated by $\simeq 1\mathrm{\mu }\mathrm{m}$. In particular, we demonstrate that the combination of electrostatic control and phase control over the ABSs increases the parameter space in which MBSs are observed. Finally, by employing an additional spectroscopic probe in the hybrid region between the quantum dots, we gain information about the spatial distribution of the Majorana wave function in a two-site Kitaev chain.

The kagome metal ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$ exhibits an unusual charge-density-wave (CDW) order, where the emergence of loop current order that breaks time-reversal symmetry (TRS) has been proposed. A key feature of this CDW phase is a nonmonotonic Hall effect at low fields, often attributed to TRS breaking. However, its origin remains unclear. Here, we conduct comprehensive magnetotransport measurements on ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$ and, through mobility spectrum analysis, identify the formation of tiny Fermi pockets with extremely high mobility below the CDW transition. Furthermore, electron irradiation experiments reveal that the nonmonotonic Hall effect is significantly suppressed in samples with reduced mobility, despite no substantial change in the electronic structure. These results indicate that the nonmonotonic Hall effect originates from these tiny Fermi pockets with high mobility carriers rather than anomalous Hall mechanisms, providing new insights into understanding the Hall anomaly in this kagome system.

Compact free-electron lasers (FELs) based on plasma-based accelerators have been envisioned for many years. While recent milestone experiments have demonstrated feasibility, further progress is needed to establish laser-plasma-accelerator-driven FELs as reliable light sources. Demonstrating both full FEL saturation and reliable operation commensurate with conventional FEL facilities is critical. We report progress on both of these fronts. FEL gain exceeding 1000 at a wavelength of 420 nm in the self-amplified spontaneous emission regime has been measured. Lower and upper bounds for the characteristic exponential gain length were measured at 16.7–22.5 cm. Additionally, reliability of the laser-plasma-accelerator-driven FEL, defined here as the percentage of shots displaying FEL gain, reached an unprecedented level of greater than 90% over the course of an hour while operating at 1 Hz repetition rate.

We propose and analyze a family of approximately symmetric neural networks for quantum spin liquid problems. These tailored architectures are parameter efficient, scalable, and significantly outperform existing symmetry-unaware neural network architectures. Utilizing the mixed-field toric code and PXP Rydberg Hamiltonian models, we demonstrate that our approach is competitive with state-of-the-art tensor network and quantum Monte Carlo methods. Moreover, at the largest system sizes ($N=480$ for toric code, $N=1584$ for Rydberg PXP), our method allows us to explore Hamiltonians with sign problems beyond the reach of both quantum Monte Carlo and finite-size matrix-product states. The network comprises an exactly symmetric block following a nonsymmetric block, which we argue learns a transformation of the ground state analogous to quasiadiabatic continuation. Our Letter paves the way toward investigating quantum spin liquid problems within interpretable neural network architectures.

Entanglement purification is to distill high-quality entanglement from low-quality entanglement. Entanglement purification determines the efficiency and communication rates and plays a key role in quantum repeaters and long-distance quantum communications. Existing entanglement purification protocols and proof of principle experiments usually choose two identical input pairs. They are limited to focus on the successful purification case to obtain high-quality entangled states and discard the remained items if the purification fails. Recent entanglement purification theory [Opt. Express 28, 2291 (2020)] for arbitrary nonidentical input mixed states indicated that the discarded items may have residual entanglement and can be reused to increase the yield of entanglement purification, while the successful purification may not obtain a high-quality entangled state. In this Letter, using hyperentanglement, we design and experimentally demonstrate an entanglement purification protocol with nonidentical input mixed states. For the first time, we experimentally confirm the existence of residual entanglement in different error models. Furthermore, we illustrate that successful purification may decrease the fidelity of purified entangled states. We also demonstrate the approach of optimal entanglement purification. Our proof of principle results have potential applications in future high-efficiency and long-distance quantum communication.

The electronic band gap of a two-dimensional semiconductor within a device architecture is sensitive to variations in screening properties of adjacent materials in the device and to gate-controlled doping. Here, we employ microfocused angle-resolved photoemission spectroscopy to separate band gap renormalization effects stemming from environmental screening and electron doping during in situ gating of a single-layer ${\mathrm{WS}}_2$ device. The ${\mathrm{WS}}_2$ is supported on hexagonal boron nitride and contains a section that is exposed to vacuum and another section that is encapsulated by a graphene contact. We directly observe the doping-induced semiconductor-metal transition and band gap renormalization in the two sections of ${\mathrm{WS}}_2$. Surprisingly, a larger band gap renormalization is observed in the vacuum-exposed section than in the graphene-encapsulated—and thus ostensibly better screened—section of the ${\mathrm{WS}}_2$. Using $GW$ calculations, we determine that intrinsic screening due to stronger doping in vacuum-exposed ${\mathrm{WS}}_2$ exceeds the external environmental screening in graphene-encapsulated ${\mathrm{WS}}_2$.

The scattering matrix $S$ linearly relates the vector of incoming waves to outgoing wave excitations, and contains an enormous amount of information about the scattering system and its connections to the scattering channels. Time delay is one way to extract information from $S$, and the transmission time delay ${\tau }_T$ is a complex (even for Hermitian systems with unitary scattering matrices) measure of how long a wave excitation lingers before being transmitted. The real part of ${\tau }_T$ is a well-studied quantity, but the imaginary part of ${\tau }_T$ has not been systematically examined experimentally, and theoretical predictions for its behavior have not been tested. Here we experimentally test the predictions of Asano et al. [Nat. Commun. 7, 13488 (2016)] for the imaginary part of transmission time delay in a nonunitary scattering system. We utilize Gaussian time-domain pulses scattering from a two-port microwave graph supporting a series of well-isolated absorptive modes to show that the carrier frequency of the pulses is changed in the scattering process by an amount in agreement with the imaginary part of the independently determined complex transmission time delay, $\mathrm{Im}[{\tau }_T]$, from frequency-domain measurements of the subunitary $S$ matrix. Our results also generalize and extend those of Asano et al., establishing a means to predict pulse propagation properties of non-Hermitian systems over a broad range of conditions.

Moiré superlattices enable engineering of correlated quantum states through tunable periodic potentials, where twist angle controls periodicity but dynamic potential strength modulation remains challenging. Here, we develop a high-pressure quantum transport technique for van der Waals heterostructures, achieving the ultimate pressure limit ($\sim 9\mathrm{GPa}$) in encapsulated moiré devices. In aligned graphene/h-BN, we demonstrate that pressure induces a substantial enhancement of the moiré potential strength, evidenced by the suppression of the first valence bandwidth and the near-doubling of the primary band gap. Moreover, we report the first observation of a tertiary gap emerging above 6.4 GPa, verifying theoretical predictions. Our results establish hydrostatic pressure as a universal parameter to reshape moiré band structures. By enabling quantum transport studies at previously inaccessible pressure regimes, this Letter expands the accessible parameter space for exploring correlated phases in moiré systems.

Phosphorene has attracted extensive research interest due to its anisotropic properties with rich tunabilities such as strongly layer-dependent and field-tunable band gaps. Revealing how the electronic structure evolves down to monolayer is critical for understanding its anisotropic properties and field tunability. Here, we report the hitherto unexplored electronic structure of monolayer phosphorene, as well as field tunability in few-layer phosphorene. A strongly enhanced mass anisotropy is observed in monolayer phosphorene, which clearly distinguishes it from bilayer and thicker flakes. Moreover, by introducing an external electric field upon doping, modifications of the mass anisotropy and energy spacing between subbands in few-layer phosphorene are further revealed. Our work reveals the unique electronic structure of monolayer phosphorene, highlighting the critical roles of interlayer coupling as well as external electric field in tailoring the band parameters in phosphorene.