An effective way to design structured coherent wave interference patterns that builds on the theory of coherent lattices, is presented. The technique combines prime number factorization in the complex plane with moiré theory to provide a robust way to design structured patterns with variable spacing of intensity maxima. In addition, the proposed theoretical framework facilitates an elegant computation of previously unexplored high-order superlattices both for the periodic and quasiperiodic case. A number of beam configurations highlighting prime examples of patterns for lattices with three-, four-, and fivefold symmetry are verified in a multibeam interference experiment.

We study the nozzle-free ejection of liquid droplets at controlled angles from a sessile drop actuated from two, mutually opposed directions by focused surface acoustic waves with dissimilar parameters. Previous researchers assumed that jets formed in this way are limited by the Rayleigh angle. However, when we carefully account for surface tension in addition to the driving force, acoustic streaming, we find a quantitative model that reduces to the Rayleigh angle only when inertia is dominant, and suggests larger ejection angles are possible in many practical situations. We confirm this in demonstrating ejection at more than double the Rayleigh angle. Our model explains the effects of both fluid and input parameters on experiments with a range of liquids. We extract, from this model, a dimensionless number that serves as an analog for the typical Weber number for predicting single droplet events.

It is well known that the acoustic properties of fluid are characterized by mass density and bulk modulus. Metafluids, the fluid metamaterials, generalize the natural fluid, which can accommodate extreme and/or negative values of these two parameters. Here, we further show that the metafluids, composed of periodic thin-walled hollow cylinders immersed in fluid, can provide not only the designable effective mass density and bulk modulus, but also a completely new effective parameter, which appears in the wave velocities as a role similar to the shear modulus of solid. The new effective parameter, describing the response of the fluid to the quadrupolar component of waves, is obtained by generalizing the effective medium theory (EMT) to include the second-order effects, which is vanishing and neglected in the conventional EMT, but giant here in the metafluids with built-in quadrupolar resonances. With the discovery of the metafluids of shearlike moduli, our Letter extends the concept of metafluids and will have a great significance in the field of metamaterials.

We propose a microphysical theory of the triboelectric effect by which mechanical rubbing separates charges across the interface between two materials. Surface electrons are treated as an open system coupled to two baths, corresponding to the bulks. Extending Zel’dovich’s theory of bosonic superradiance, we show that motion-induced population inversion can generate an electromotive force. We argue that this is consistent with the basic phenomenology of triboelectrification and triboluminescence as irreversible processes, and we suggest how to carry out more precise experimental tests.

We report the nanoscale conductivity imaging of correlated electronic states in angle-aligned ${\mathrm{WSe}}_2/{\mathrm{WS}}_2$ heterostructures using microwave impedance microscopy. The noncontact microwave probe allows us to observe the Mott insulating state with one hole per moiré unit cell that persists for temperatures up to 150 K, consistent with other characterization techniques. In addition, we identify for the first time a Mott insulating state at one electron per moiré unit cell. Appreciable inhomogeneity of the correlated states is directly visualized in the heterobilayer region, indicative of local disorders in the moiré superlattice potential or electrostatic doping. Our work provides important insights on 2D moiré systems down to the microscopic level.

We report new oscillations of wave packets in quantum walks subjected to electric fields, that decorate the usual Bloch-Zener oscillations of insulators. The number of turning points (or suboscillations) within one Bloch period of these oscillations is found to be governed by the winding of the quasienergy spectrum. Thus, this provides a new physical manifestation of a topological property of periodically driven systems that can be probed experimentally. Our model, based on an oriented scattering network, is readily implementable in photonic and cold atomic setups.

Elucidating the orbital level origin of second harmonic generation (SHG) in materials and identifying the local contributions is a long-standing challenge. We report a first principles approach for the SHG where the contributions from individual orbitals or atoms can be evaluated via symmetry adapted Wannier functions without semiempirical parameters. We apply this method to the common SHG materials ${\mathrm{KBe}}_2{\mathrm{BO}}_3{\mathrm{F}}_2$, ${\mathrm{KCaCO}}_3\mathrm{F}$, and $\beta \text{−}{\mathrm{BaB}}_2{\mathrm{O}}_4$, and show that the orbitals on noncentrosymmetric sublattices are responsible for SHG effect and the energies of these orbitals control the magnitude.

Dynamically encircling exceptional points (EPs) can lead to chiral mode switching as the system parameters are varied along a path that encircles EP. However, conventional encircling protocols result in low transmittance due to path-dependent losses. Here, we present a paradigm to encircle EPs that includes fast Hamiltonian variations on the parameter boundaries, termed Hamiltonian hopping, enabling ultrahigh-efficiency chiral mode switching. This protocol avoids path-dependent loss and allows us to experimentally demonstrate nearly 90% efficiency at 1550 nm in the clockwise direction, overcoming a long-standing challenge of non-Hermitian optical systems and powering up new opportunities for EP physics.

The Vicsek model of self-propelled particles is known in three different phases: a polar ordered homogeneous phase, also called the Toner-Tu phase, a phase of polar ordered regularly arranged high density bands with surrounding low density regions without polar order, and a homogeneous phase without polar order. Here, we show that the standard Vicsek model has a fourth phase for large system sizes: a polar ordered cross sea phase. We demonstrate that the cross sea phase is not just a superposition of two waves, but it is an independent complex pattern with an inherently selected crossing angle.

Electrical double layers (EDLs) play a significant role in a broad range of physical phenomena related to colloidal stability, diffuse-charge dynamics, electrokinetics, and energy storage applications. Recently, it has been suggested that for large ion sizes or multivalent electrolytes, ions can arrange in a layered structure inside the EDLs. However, the widely used Poisson–Boltzmann models for EDLs are unable to capture the details of ion concentration oscillations and the effect of electrolyte valence on such oscillations. Here, by treating a pair of ions as hard spheres below the distance of closest approach and as point charges otherwise, we are able to predict ionic layering without any additional parameters or boundary conditions while still being compatible with the Poisson–Boltzmann framework. Depending on the combination of ion valence, size, and concentration, our model reveals a structured EDL with spatially oscillating ion concentrations. We report the dependence of critical ion concentration, i.e., the ion concentration above which the oscillations are observed, on the counter-ion valence and the ion size. More importantly, our model displays quantitative agreement with the results of computationally intensive models of the EDL. Finally, we analyze the nonequilibrium problem of EDL charging and demonstrate that ionic layering increases the total charge storage capacity and the charging timescale.

We introduce and study a novel class of sensors whose sensitivity grows exponentially with the size of the device. Remarkably, this drastic enhancement does not rely on any fine-tuning, but is found to be a stable phenomenon immune to local perturbations. Specifically, the physical mechanism behind this striking phenomenon is intimately connected to the anomalous sensitivity to boundary conditions observed in non-Hermitian topological systems. We outline concrete platforms for the practical implementation of these non-Hermitian topological sensors ranging from classical metamaterials to synthetic quantum materials.

The nanostructure of hydrogenated amorphous silicon (a-$\mathrm{Si}:\mathrm{H}$) is studied by a combination of small-angle x-ray scattering (SAXS) and small-angle neutron scattering (SANS) with a spatial resolution of 0.8 nm. The a-$\mathrm{Si}:\mathrm{H}$ materials were deposited using a range of widely varied conditions and are representative for this class of materials. We identify two different phases that are embedded in the a-$\mathrm{Si}:\mathrm{H}$ matrix and quantified both according to their scattering cross sections. First, 1.2 nm sized voids (multivacancies with more than 10 missing atoms) which form a superlattice with 1.6 nm void-to-void distance are detected. The voids are found in concentrations as high as $6\times {10}^{19}{\mathrm{cm}}^{-3}$ in a-$\mathrm{Si}:\mathrm{H}$ material that is deposited at a high rate. Second, dense ordered domains (DOD) that are depleted of hydrogen with 1 nm average diameter are found. The DOD tend to form 10–15 nm sized aggregates and are largely found in all a-$\mathrm{Si}:\mathrm{H}$ materials considered here. These quantitative findings make it possible to understand the complex correlation between structure and electronic properties of a-$\mathrm{Si}:\mathrm{H}$ and directly link them to the light-induced formation of defects. Finally, a structural model is derived, which verifies theoretical predictions about the nanostructure of a-$\mathrm{Si}:\mathrm{H}$.

Recently, two-dimensional layered electrides have emerged as a new class of materials which possess anionic electrons in the interstitial spaces between cationic layers. Here, based on first-principles calculations, we discover a time-reversal-symmetry-breaking Weyl semimetal phase in a unique two-dimensional layered ferromagnetic (FM) electride ${\mathrm{Gd}}_2\mathrm{C}$. It is revealed that the crystal field mixes the interstitial electron states and $\mathrm{Gd}\text{−}5d$ orbitals near the Fermi energy to form band inversions. Meanwhile, the FM order induces two spinful Weyl nodal lines (WNLs), which are converted into multiple pairs of Weyl nodes through spin-orbit coupling. Further, we not only identify Fermi-arc surface states connecting the Weyl nodes but also predict a large intrinsic anomalous Hall conductivity due to the Berry curvature produced by the gapped WNLs. Our findings demonstrate the existence of Weyl fermions in the room-temperature FM electride ${\mathrm{Gd}}_2\mathrm{C}$, therefore offering a new platform to investigate the intriguing interplay between electride materials and magnetic Weyl physics.

We explore the relationship between symmetrization and entanglement through measurements on few-particle systems in a multiwell potential. In particular, considering two or three trapped atoms, we measure and distinguish correlations arising from two different physical origins: antisymmetrization of the fermionic wave function and interaction between particles. We quantify this through the entanglement negativity of states, and the introduction of an antisymmetric negativity, which allows us to understand the role that symmetrization plays in the measured entanglement properties. We apply this concept both to pure theoretical states and to experimentally reconstructed density matrices of two or three mobile particles in an array of optical tweezers.

Spectroscopy is an important tool for probing the properties of materials, chemicals, and biological samples. We design a practical transmitter-receiver system that exploits entanglement to achieve a provable quantum advantage over all spectroscopic schemes based on classical sources. To probe the absorption spectra, modeled as a pattern of transmissivities among different frequency modes, we employ broadband signal-idler pairs in two-mode squeezed vacuum states. At the receiver side, we apply photodetection after optical parametric amplification. Finally, we perform a maximum likelihood decision test on the measurement results, achieving an error probability orders of magnitude lower than the optimum classical systems in various examples, including “wine tasting” and “drug testing” where real molecules are considered. In detecting the presence of an absorption line, our quantum scheme achieves the optimum performance allowed by quantum mechanics. The quantum advantage in our system is robust against noise and loss, which makes near-term experimental demonstration possible.

Quantum correlations in observables of multiple systems not only are of fundamental interest, but also play a key role in quantum information processing. As a signature of these correlations, the violation of Bell inequalities has not been demonstrated with multipartite hybrid entanglement involving both continuous and discrete variables. Here we create a five-partite entangled state with three superconducting transmon qubits and two photonic qubits, each encoded in the mesoscopic field of a microwave cavity. We reveal the quantum correlations among these distinct elements by joint Wigner tomography of the two cavity fields conditional on the detection of the qubits and by test of a five-partite Bell inequality. The measured Bell signal is $8.381\pm 0.038$, surpassing the bound of 8 for a four-partite entanglement imposed by quantum correlations by 10 standard deviations, demonstrating the genuine five-partite entanglement in a hybrid quantum system.

The current understanding of aging phenomena is mainly confined to the study of systems with short-ranged interactions. Little is known about the aging of long-ranged systems. Here, the aging in the phase-ordering kinetics of the two-dimensional Ising model with power-law long-range interactions is studied via Monte Carlo simulations. The dynamical scaling of the two-time spin-spin autocorrelator is well described by simple aging for all interaction ranges studied. The autocorrelation exponents are consistent with $\lambda =1.25$ in the effectively short-range regime, while for stronger long-range interactions the data are consistent with $\lambda =d/2=1$. For very long-ranged interactions, strong finite-size effects are observed. We discuss whether such finite-size effects could be misinterpreted phenomenologically as subaging.

We introduce an equation for density matrices that ensures a monotonic decrease of the free energy and reaches a fixed point at the Gibbs thermal. We build a variational approach for many-body systems that can be applied to a broad class of states, including all bosonic and fermionic Gaussian, as well as their generalizations obtained by unitary transformations, such as polaron transformations in electron-phonon systems. We apply it to the Holstein model on $20\times 20$ and $50\times 50$ square lattices, and predict phase separation between the superconducting and charge-density wave phases in the strong interaction regime.

We study how perturbations affect dynamics of integrable many-body quantum systems, causing transition from integrability to chaos. Looking at spin transport in the Heisenberg chain with impurities we find that in the thermodynamic limit transport gets diffusive already at an infinitesimal perturbation. Small extensive perturbations therefore cause an immediate transition from integrability to chaos. Nevertheless, there is a remnant of integrability encoded in the dependence of the diffusion constant on the impurity density, namely, at small densities it is proportional to the square root of the inverse density, instead of to the inverse density as would follow from Matthiessen’s rule. We show that Matthiessen’s rule has to be modified in nonballistic systems. Results also highlight a nontrivial role of interacting scattering on a single impurity, and that there is a regime where adding more impurities can actually increase transport.

The inspiral phasing of binary black holes at intermediate mass ratios ($m_2/m_1\sim {10}^{-3}$) is important for gravitational wave observations, but not accessible to standard modeling techniques: The accuracy of the small mass-ratio (SMR) expansion is unknown at intermediate mass ratios, whereas numerical relativity simulations cannot reach this regime. This article assesses the accuracy of the SMR expansion by extracting the first three terms of the SMR expansion from numerical relativity data for nonspinning, quasicircular binaries. We recover the leading term predicted by SMR theory and obtain a robust prediction of the next-to-leading term. The influence of higher-order terms is bounded to be small, indicating that the SMR series truncated at next-to-leading order is quite accurate at intermediate mass ratios and even at nearly comparable mass binaries. We estimate the range of applicability for SMR and post-Newtonian series for nonspinning, quasicircular inspirals.