We present experimental results using a single-electron resolution skipper CCD running above ground level to demonstrate the potential of this technology for its use in reactor neutrino observations and other low-energy particle-interaction experiments. Operating conditions and event-selection criteria are provided to decouple most of the background rate at low energies. The majority of this background comes from interactions in the inactive silicon surrounding the active detector volume that ends up in the readout register of the sensor. Our final results are compared with other low-threshold technologies showing a good control of the background for low ionization energies down to five electron-hole pairs. This demonstrates that the skipper CCD proves to be among the best options to measure low-energy and weakly interacting particles at ground level.

Rapid heating is highly sought-after for compositional control in the sintering-annealing process of materials containing volatile elements. Although several innovative approaches have been reported, suitable processes for the rapid annealing of thin films are still very rare. Herein, we develop a high-temperature rapid heating method for thin-film preparation through employing an indium tin oxide (ITO)/mica-based flexible transparent heater (FTH). The ITO/mica FTH shows an extremely fast thermal response (2 s), high saturation temperature (>830 °C), and high heating-cooling rates (>${10}^4$ °C ${\min }^{-1}$). Thermodynamic analysis reveals that the excellent heating performance can be largely attributed to the high heat-transfer coefficient and the low thickness of the mica substrates. The remarkable potential of our ITO/mica FTH for practical use is unambiguously evident by the demonstration of water heating and rapid thermal annealing of ferroelectric oxide thin films.

We present a quantitative study of the nonlinear optical response of layered perovskites placed inside planar photonic microcavities in the regime of strong light-matter coupling, when excitonic and photonic modes hybridize and give rise to cavity polaritons. Two sources of nonlinearity are specified, the saturation of the excitonic transition with increase of the optical pump and Coulomb interaction between the excitons. It is demonstrated that a peculiar form of the interaction potential, specific to the multilayer structure of organic perovskites, is responsible for the substantial increase of the exciton binding energy and Rabi splitting with respect to conventional semiconductor systems. This results in a dominant contribution of the Rabi splitting quench effect in the nonlinear optical response. Moreover, due to the tightly bound character of excitons, the density of Mott transition is essentially higher, allowing extremely large polariton blueshifts of about 20 meV to be reached, which is an order of magnitude higher than in conventional semiconductors.

Digital signatures can guarantee the unforgeability and transferability of the message. Differently from classical digital signatures, whose security depends on computational complexity, quantum digital signatures (QDSs) can provide information-theoretic security. We propose a general method of random-pairing QDS, which can drastically increase QDS efficiency. In a way, our random-pairing method provides a tightened result for the security level of QDS. In the method, the parity value of each pair is used for the outcome-bit value. We present general formulas for the fraction of untagged bits and error rates of the outcome bits. Random pairing can be applied as a fundamental method to increase the QDS efficiency for all existing quantum key distribution (QKD) protocols. We take the QDS with sending-or-not-sending protocol and the QDS with side-channel-free protocol as examples to demonstrate the advantage of random pairing through numerical simulation. A similar advantage with random pairing is also found with decoy-state measurement-device-independent QKD and also the decoy-state BB84 protocol. We study the random-pairing QDS with sending-or-not-sending protocol considering effects of finite data size through optimization. The numerical simulation results show that the signature rate can be increased by more than $100\mathrm{\%}$ under a noisy channel using our random-pairing method.

Quantum annealing (QA) was originally intended for accelerating the solution of combinatorial optimization tasks that have natural encodings as Ising models. However, recent experiments on QA-hardware platforms have demonstrated that, in the operating regime corresponding to weak interactions, the QA hardware behaves like a noisy Gibbs sampler at a hardware-specific effective temperature. This work builds on those insights and identifies a class of small hardware-native Ising models that are robust to noise effects and proposes a procedure for executing these models on QA hardware to maximize Gibbs-sampling performance. The experimental results indicate that the proposed protocol results in high-quality Gibbs samples from a hardware-specific effective temperature. Furthermore, we show that this effective temperature can be adjusted by modulating the annealing time and energy scale. The procedure proposed in this work provides an approach to using QA hardware for Ising-model sampling presenting potential opportunities for applications in machine learning and physics simulation.

Supercapacitors exhibit immense potential in electric vehicles and national grids due to their high power density. The power and energy density of supercapacitors largely depend on the design of electrodes and the composition of electrolytes, which dominate the capacitive charging process. However, the availability of only a few mathematical models for capacitive charging in bulk porous electrodes has limited the rational design of a supercapacitor in practice. Herein, a mathematical model is proposed to predict the charging process in a porous electrode and is then experimentally validated. In this model, the dependence of capacitive behavior on the conductivity of both the electrode and electrolyte, as well as the porosity and thickness of electrode, are systematically discussed. Moreover, different charging modes, e.g., potentiostatic charging, potentiodynamic charging, and galvanostatic charging, are studied. The results of this model indicate that the conductivity of the electrolyte (even though it is an aqueous electrolyte) is the bottleneck that limits the charging rate of a supercapacitor, in particular, in thick electrode films. This mathematical model could be a powerful tool for optimizing the design of both electrodes and electrolytes for high-performance supercapacitors.

Photophoretic forces are induced when light causes a net momentum exchange between a particle and a surrounding gas. Such forces have been shown to be a robust means for trapping and guiding particles in air over long distances. Here, we apply the concept of an optical funnel for the delivery of bioparticles to the focus of an x-ray free-electron laser (XFEL) for femtosecond x-ray diffractive imaging. We provide the experimental demonstration of transversely compressing a high-speed beam of aerosolized viruses via photophoretic forces in a low-pressure gas environment. Relative temperature gradients induced on the viruses by the laser are estimated via particle-velocimetry measurements. The results demonstrate the potential for an optical funnel to improve particle-delivery efficiency in XFEL imaging and spectroscopy.

Vacuum-gap and orthogonally aligned double-gate geometry is employed in a nanowire-based electromechanical resonator device to independently control two nearly degenerate orthogonal vibration modes. In the device, piezoresistance is the dominant mechanism of motion-induced conductance variation, which provides an efficient scheme for the self-transduction of vibrational motion into an electric signal. Two simultaneously applied gate voltages induce an opposite combined effect on the frequency shift between two vibration modes, which is well explained by model calculations. Using the opposite double-gate effect, we demonstrate vectorial control of two mode frequencies, which is not possible with single-gate geometry.

We introduce a diffraction-theory-inspired analytical description of the metasurface comprising an array of graphene subwavelength hemispheres. Our theory describes light interaction with the random metasurface, in which the periodicity is broken by accidentally damaged meta-atoms in the nodes of a two-dimensional periodic lattice. Both numerical modeling and experiments show that such a nanometer-thin metasurface possesses giant broadband absorption in the terahertz spectral range that remains intact, even when a substantial portion of meta-atoms, i.e., graphene hemispheres, is damaged. Moreover, defective fabrication of graphene free-standing metasurface may enhance the absorptive properties.

The inhomogeneous magnetization distribution in antiskyrmions helps in nullifying the unwanted skyrmion Hall effect generally found in the current driven motion of skyrmions. At present, the observation of room-temperature antiskyrmion phase is limited to only a very few materials. Here, we present the evidence of a tunable antiskyrmion phase in the $D_{2d}$-symmetry-based tetragonal Heusler system ${\mathrm{Mn}}_{2+x}{\mathrm{Ni}}_{1-x}\mathrm{Ga}$. With the help of dc magnetization, ac susceptibility, and topological Hall effect measurements, we demonstrate that the potential antiskyrmion phase can be tuned over a wide compositional range with magnetic ordering temperature of above 600 K. In addition, we find the existence of multiple topological phase transitions for a certain Mn/Ni ratio where the magnetic anisotropy attains its maxima. Our micromagnetic simulations suggest that the transition from antiskyrmionium and antiskyrmion pockets to the conventional antiskyrmion phase at the optimal value of magnetic anisotropy might be responsible for the observed multiple topological transitions in the present materials. The expected small size of antiskyrmions in the present low magnetic-moment-based ferrimagnetic system gives a great advantage over other skyrmion and antiskyrmion hosting materials for their potential application in racetrack-based memory devices.

Magnetic skyrmions form in chiral multilayers from the shrinking or fission of elongated stripe textures. Here we report an experimental and theoretical study of the temperature dependence of this stripe-to-skyrmion transition in $\mathrm{Co}$/$\mathrm{Pt}$-based multilayers. Field-reversal magnetometry and Lorentz microscopy experiments over 100–350 K establish the increased efficacy of stripe-to-skyrmion fission at higher temperatures—driven primarily by the thermal evolution of key magnetic interactions—which enhances the resulting skyrmion density. Atomistic calculations elucidate that the energy barrier to fission governs the thermodynamics of skyrmion formation. Our results establish a mechanistic picture of the stripe-to-skyrmion transition and advance the use of thermal knobs for efficient skyrmion generation.

Spin waves are promising chargeless information carriers for the future, energetically efficient beyond CMOS systems. Among many advantages are the ease of achieving nonlinearity, the variety of possible interactions, and excitation types. Although the rapidly developing magnonic research has already yielded impressive realizations, multimode nonlinear effects, particularly with propagating waves and their nanoscale realizations, are still an open research problem. We theoretically study the dynamic interactions of spin waves confined to the edge of a thin ferromagnetic film with the spin-wave beam incident at this edge. We find inelastically scattered spin-wave beams at frequencies increased and decreased by the frequency of the edge spin-wave relative to the specularly reflected beam. We observe a strong dependence of the angular shift of the inelastic scattered spin-wave beam on the edge-mode frequency, which allows us to propose a magnonic demultiplexing of the signal encoded in spin waves propagating along the edge. Since dynamic magnetostatic interactions, which are ubiquitous in the spin-wave dynamics, are decisive in this process, this indicates the possibility of implementing the presented effects in other configurations and their use in magnonic systems.

We propose the design of a flat active wall panel and demonstrate its effectiveness in modulating the wall impedance, which can lead to the total absorption of incident sound waves in the low-frequency range of 50–120 Hz, or alter its reflection phase. Such an acoustic frequency range is usually the most difficult to handle for passive acoustic components, owing to the long wavelength, and consequently, the bulky size of the materials required. The active panel is actuated by a piezoelectric transducer, with its vibrational displacement amplified by a specially designed mechanical amplifier. Through both simulations and impedance-tube experiments, we show that simply tuning the active panel’s displacement amplitude can vary its impedance from that of the hard wall, to impedance matching with air (leading to total absorption), to zero (leading to reflection phase reversal). No feedback loop is necessary for the active-panel device; only an initial adjustment during installation is necessary. We simulate the room-acoustics application for a 1 × 1 ${\mathrm{m}}^2$ wall panel that occupies only 1/48 of the total wall area of the room and show that it can introduce switchable elements to the audio experience.

We investigate dissipative nonlinear dynamics in graphene-based active metamaterials composed of randomly dispersed graphene nanoflakes embedded within an externally pumped gain medium. We observe that graphene saturable nonlinearity produces a subcritical bifurcation of nonlinear modes, enabling self-organization of the emitted radiation into several dissipative soliton structures with distinct topological charges. We systematically investigate the existence domains of such nonlinear waves and their spatial dynamics, finding that soliton vortices are unstable, thus enabling self-organization into single dissipative structures with vanishing topological charge, independently of the shape of the graphene nanoflakes. Our results shed light on self-organization of coherent radiation structures in disordered systems and are relevant for future cavity-free lasers and amplifier designs.

Periodic structures composed of quarter-wavelength or Helmholtz resonators have been widely used in the design of acoustic metamaterials. An interesting phenomenon achievable through hybridization in such structures is the slow sound, which results from the strong dispersion produced by the local resonances. It gives rise to many applications such as deep subwavelength sound absorbers or metadiffusers. All the applications proposed so far have been analyzed only in the frequency domain (steady state). In this work, we propose a passive treatment that can be used in room acoustics, which requires considering the time domain and all multiple reflections. We analytically design a delay line from a metasurface made of Helmholtz resonators, using slow-sound propagation. We prove numerically and experimentally that such structures can delay a pulse and thus reproduce the sound perception of a propagation over a given distance, larger than the actual size of the treatment. The limitations of real-time pulse propagation, dispersion, and losses on audio fidelity are discussed.

Recent research on hybrid magnonics has been restricted by the long magnon wavelengths of the ferromagnetic resonance modes. We present an experiment on the hybridization of 250-nm-wavelength magnons with microwave photons in a multimode magnonic system consisting of a planar cavity and a magnetic bilayer. The coupling between magnon modes in the two magnetic layers, i.e., the uniform mode in Permalloy and the perpendicular standing spin waves (PSSWs) in yttrium iron garnet, serves as an effective means for exciting short-wavelength PSSWs, which is further hybridized with the photon mode of the microwave resonator. The demonstrated magnon-photon coupling approaches the superstrong coupling regime, and can even be achieved near zero bias field.

Elusive features in photonic and electronic devices can be detected by means of advanced, time-domain spectroscopic techniques. In this paper we introduce a modulation spectroscopy based on the optomechanical interaction of photonic and mechanical modes. Applying the technique to a $\mathrm{Si}$ metasurface and its drumlike mechanical modes, we detect narrow-band quasi-bound-state-in-the-continuum (quasi-BIC) modes close to normal incidence, where their measurement can be hindered by a high-symmetry protection and undesired background modes. Showing a visibility enhancement of more than one order of magnitude, the optomechanical modulation spectroscopy can be an innovative tool for precise spectroscopy of a wide set of photonic devices, including the goal of measuring purely symmetry protected BIC resonances.

Lattice structures can exhibit unusual mechanical properties by appropriate design and arrangement of the microstructures, and have already found applications in areas such as tissue engineering, stretchable electronics, and soft robotics. However, the designed microstructures generally follow simple geometric patterns with constant curvatures and theoretical models are developed for each geometry particularly. It lacks a universal method to model and design the periodic lattice constructed from microstructures with varying curvatures. In this paper, we develop a universal approach to design polygonal lattices with a wide range of microstructures with varying curvatures using instant curvature and parametric functions. A finite deformation model is proposed for the microstructures and the corresponding lattices, which considers the wavy or curled microstructure, hierarchical geometry, and large deformation. Experiments and finite-element simulations are conducted to validate the theoretical model. All of Young’s modulus, stretchability, and Poisson’s ratio can be inversely designed using the developed theoretical model. Results show that the stretchability of the highly stretchable lattice can be further increased by more than 4 times using densely curled microstructure. The signs of Poisson’s ratio can also change with the axial strain by rationally designing the microstructures. By combining curve fitting and curvature and parametric functions, the mechanical behaviors of lattices constructed by bioinspired microstructures can also be predicted. The lattice structures are then demonstrated to reinforce a hydrogel with modulus increased by around 2 orders and act as a biomimetic soft-strain sensor. This work could aid the design of a hierarchical lattice and have potential applications in tissue engineering, stretchable electronics, and soft robotics.

${90}^{\circ }$ pinned magnetic domain walls can be observed in thin magnetic layers attached to a ferroelectric substrate. The main stabilization mechanism of the noncollinear magnetic texture is the strain transfer, which is responsible for imprinting of the ferroelectic domains into the uniaxial anisotropy of the ferromagnet. Here, we investigate by means of micromagnetic simulations how the interfacial Dzyaloshinskii-Moriya interaction influences the ${90}^{\circ }$ domain-wall structure. It is shown that Dzyaloshinskii-Moriya interaction induces a large out-of-plane magnetization component, strongly dependent on the domain wall type. In particular, it is shown that this out-of-plane magnetization component is crucial for the transport of the in-plane magnetic skyrmions, also known as bimerons, through the magnetic domain walls. Based on the results of micromagnetic simulations, a concept of in-plane magnetic skyrmion valve based on two ${90}^{\circ }$ pinned magnetic domain walls is introduced.