Wire medium (WM) resonators have emerged as a promising realization for plasma haloscopes—devices designed to detect axions, a potential component of dark matter. Key factors influencing the detection probability include cavity volume, resonance quality factor, and form factor. While the form factor has been explored for resonant frequency tuning, its optimization for axion detection remains unexplored. In this work, we present an approach to significantly enhancing the form factor of WM plasma haloscopes. By shifting the metal walls of the resonator by a quarter wavelength, we effectively convert an electric wall boundary condition into a magnetic wall one, allowing for an almost uniform mode. Theoretical analysis and numerical simulations confirm that this modification improves the electric field profile and boosts the form factor, while also slightly enhancing the quality factor. We validate these findings through experimental results from two prototype resonators: one with a standard geometry and another with a quarter-wave air gap between the WM and the walls. Additionally, our method provides a simple way to control the field profile within WM cavities, which can be explored for further applications.

Superconducting radio-frequency (SRF) niobium cavities are critical for modern particle accelerators, as well as for advancing superconducting quantum systems and enabling ultrasensitive searches for new physics. In this work, we report a systematic observation of an anomalous frequency dip in $\mathrm{Nb}$ cavities, which occurs at temperatures just below the critical temperature ($T_c$), indicative of enhanced superconducting properties at $T\ll T_c$. The magnitude of this dip is strongly correlated with the rf surface resistance, impurity distribution near the surface, and $T_c$. Additionally, we report measurements of the coherence peak in the ac conductivity of two $\mathrm{Nb}$ SRF cavities processed using distinct methods. By comparing recent theories developed to model this experimental data, we show that the frequency-dip feature, larger coherence peak height, and reduction in the temperature-dependent surface resistance with rf current occur at minimal but finite levels of disorder.

Progress in the fabrication of nanoscale systems based on the two-dimensional electron gas (2DEG) at the interface between ${\mathrm{La}\mathrm{Al}\mathrm{O}}_3$ and ${\mathrm{Sr}\mathrm{Ti}\mathrm{O}}_3$ (LAO/STO) has created increased demand for simulations of these nanostructures, which typically range in size from tens to hundreds of nanometers. Due to the low lattice constant of LAO/STO, approximately 0.39 nm, these calculations become extremely time-consuming. Here, we present a scaling procedure for the tight-binding approximation of the LAO/STO 2DEG, defined on a square lattice that can be several times larger than in the conventional approach. The scaled model is analyzed within the context of quantum transport simulations and electronic structure calculations. Our findings demonstrate that the scaled model closely aligns with the ordinary one up to a scaling factor of 8. The applicability of the scaled Hamiltonian for systems with interacting electrons is also discussed. These results pave the way for more efficient simulations of LAO/STO nanostructures with realistic sizes relevant to experimental applications.

The treatment efficacy for numerous human diseases relies on the early diagnosis of tissue pathologies. Some of the associated microscopic histopathological features (e.g., abnormal shape and organization of cells) affect the propagation of light through the tissue, rendering many optical techniques potential screening tools. In this context of early detection and screening, optical techniques that allow highly localized (i.e., microscopic) probing of such light-tissue interaction are most promising: their small interrogation volumes eliminate the influence of the surrounding healthy tissue, thereby rendering these techniques highly sensitive to small superficial lesions. Leveraging this sensitivity in the determination of tissue status, however, necessitates a theoretical light-transport framework (relating the optical signal changes to histopathology). This has so far remained elusive, as the optical signals generally comprise contributions from two distinct light-transport regimes (i.e., subdiffuse and diffuse), stymieing the formulation of a unified theory. Consequently, current models are either empirical or rely on limiting assumptions regarding light propagation (in turn restricting the model validities). Here, we develop and propose the use of a powerful computational framework (which inherently consolidates the subdiffuse and diffuse light-transport regimes) to model such optical signals and theoretically validate and demonstrate the practical feasibility of this approach.

Understanding the ability of salts to crystallize at the interface between two porous media with different material properties is of paramount importance to understanding the more complex real-world degradation mechanisms associated with salt crystallization in composite materials and the causes of the delamination of ceramics, tiles, and mural paintings. We present our results on salt crystallization at the interface between hydrophilic and hydrophobic porous media during the evaporation of aqueous salt solutions. For this purpose, we design artificial 2D monolayer porous media to study the fundamentals of crystallization at the interface of two porous materials with different wettability properties at the microscale, and we compare the results with 3D samples to show the scalability of the process. In the experiments, the drying kinetics and dynamics of salt precipitation (sodium chloride and sodium sulfate) are studied in real time using optical microscopy with image analysis or x-ray microtomography combined with mass-change monitoring during evaporation. Our study reveals how the interface between different wettability regions, combined with the interfacial properties of the precipitating crystals, impacts the drying kinetics and the crystallization dynamics of the salt solution. Depending on the salt, precipitated crystals can either block the interface and prevent the samples from drying or form subflorescence in the hydrophilic region, potentially causing further damage. Understanding the material dynamics in the presence of salt and hydrophobic treatments helps with the development of more adequate solutions for the conservation of multilayered composite artworks.

In wireless power transfer systems, robust transfer efficiency under various operating conditions remains a fundamentally important challenge. This becomes even more critical when transferring power to groups of inductively coupled receivers. We propose a method for efficient wireless power transfer to multiple receivers, exploiting the concept of exceptional points of degeneracy (EPDs) in a self-oscillating system. In previous studies based on parity-time ($\mathcal{P}\mathcal{T}$) symmetry, a receiver’s operation has been divided into the strong and weak coupling regimes, and the power transfer efficiency is constant in the strong coupling regime when varying the coupling factor. Here, the concept of strong and weak coupling and constant power transfer efficiency is extended to a system of multiple receivers that do not follow $\mathcal{P}\mathcal{T}$ symmetry. The transmitter has saturable nonlinear gain, and the EPD is analyzed when the system oscillates after reaching saturation. We show that the important feature for achieving roughly constant power transfer efficiency independent of the positions of the receivers, is the existence of an EPD that separates the weak and strong coupling regimes. Our proposed method produces a system with less sensitivity to changes in coupling than a conventional system without an EPD when the receivers and their couplings to the transmitter are not necessarily identical.

In this work, we present a quantum theory for pulsed photon pair generation in a single ring resonator. Our approach combines the Heisenberg picture input-output formalism with the Ikeda mapping from classical nonlinear optics. In doing so, we address the high-gain regime by incorporating nonperturbative effects, including self-phase modulation, cross-phase modulation, and time-ordering, which are roots for significantly different behaviors in the low-gain regime. We also account for optical losses by introducing an auxiliary waveguide, allowing for a more accurate representation of experimentally viable scenarios. Numerical simulations reveal that nonperturbative effects significantly distort transfer functions, making desirable operations challenging without careful optimization. We show that appropriate detuning of the pump frequency can mitigate these issues, leading to enhanced brightness and higher spectral purity in the high-gain regime. We further investigate the performance of a single ring resonator as a two-mode squeezer by analyzing various performance metrics under experimentally relevant optical loss conditions.

Advances in research in fields such as quantum information and quantum chemistry require subtle methods for trapping particles, including ions, neutral atoms, and molecules. Here, we propose a hybrid ion-trapping method that combines a Paul trap with optical tweezers. This trap incorporates both the deep-potential characteristic of the Paul trap and the micromotion-free nature of the optical dipole trap. By modulating the optical dipole trap synchronously with the radio-frequency voltage of the Paul trap, the alternating electrical force in the trap center is fully counteracted, and the micromotion temperature of a cold trapped ion can reach the nanokelvin scale, while the trap depth exceeds 300 K. These features will allow cold collisions between an ion and an atom in the $s$-wave regime and stably trap the produced molecular ion in the cold hybrid system. This provides a unique platform for probing the interactions between the ions and the surrounding neutral particles and enables the investigation of new reaction pathways and reaction products in the cold regime.

Neuromorphic computing aims to revolutionize large-scale data processing by developing efficient methods and devices inspired by neural networks. Among these, the control of magnetism through ion migration has emerged as a promising approach due to the inherent memory and nonlinearity of ionically conducting and magnetic materials. In this work, we present a lithium-ion-based magneto-ionic device that uses applied voltages to control the magnetic domain state of a perpendicularly magnetized ferromagnetic layer. This behavior emulates the analog and nonvolatile properties of biological synapses and enables the creation of a simple reservoir computing system. To illustrate its capabilities, the device is used in a waveform classification task, where the voltage amplitude range and magnetic bias field are tuned to optimize the recognition accuracy.

Real-world experiments on quantum systems are always performed with measurement apparatus whose interaction times with the systems are finite. This restricts the observable quantum states to the space of time-coarse-grained density matrices $\{\overline{\rho }(t)\}$, providing motivation for the time-coarse-graining (TCG) approach that solves for $\overline{\rho }(t)$ without ever referring to the unobservable $\rho (t)$ of infinite time resolution. Phenomenologically, this implies that coherent transitions far outside the bandwidth would be filtered out, leaving only their effective impacts on the “slow” dynamics resolvable by the finite time resolution of the measurements. Therefore, the TCG framework provides rigorous justification for many existing effective Hamiltonian methods in the literature that aim at capturing the unitary part of the long-time dynamics. However, since time-coarse-graining is fundamentally irreversible, the resulting effective model allows for secular loss of information and dissipation of energy in general, which cannot be captured by any unitary effective models and has to be treated with explicit time-coarse-graining. Such incoherent effects are particularly prominent in driven nonlinear quantum systems where exchange of information and energy with the drive gives rise to incoherent effective dynamics at all finite time resolutions in general. While rigorous in principle, existing TCG methods in the literature can be applied only to simple systems by one iteratively solving superoperator equations at low orders in the coupling strengths. The complexity of such methods prevents systematic study of the time-coarse-grained dynamics and limits analytical results to the IR (low-resolution) limit in most cases. We address these limitations in this paper, presenting a systematic time-coarse-graining method that overcomes the complexities and restrictions of current techniques, offering a comprehensive and accurate modeling framework for driven nonlinear quantum systems. We derive closed-form formulas as well as diagrammatic representations for both unitary and nonunitary contributions, in the form of an effective Hamiltonian and nonunitary dissipators at arbitrary order in the coupling strengths, and complement this with a computer-algebra software package. We demonstrate the effectiveness of the method using several typical models of driven nonlinear systems in superconducting circuits, and show that it generalizes and improves on existing methods by providing more accurate results and explaining phenomena that have not been accounted for.

Topological physics in electromagnetics has enabled topological edge-state waveguides, yet traditional propagation path designs of topological photonics are restricted by the geometry of the underlying periodic lattice. Here, we propose a topological waveguide scheme based on Voronoi diagrams, allowing for arbitrary propagation paths and offering greater flexibility beyond the constraints of conventional periodic structures. Focusing on gyromagnetic photonic topological insulators and valley topological insulators, we detail the construction and implementation process. Our method ensures smooth connections between unit cells and efficient wave transmission, which are validated through both simulations and experiments. The proposed scheme greatly expands the flexibility for topological transport and enables more applications for complex topological devices and systems.

The successful development of ferromagnetic nematic liquid crystals (FNLCs) has opened up a new direction for research in liquid crystals, which has the potential for technological applications. Previous research has predominantly focused on FNLCs based on positive dielectric anisotropy liquid crystals. In this paper, we report the preparation and comprehensive characterization of an FNLC with low birefringence and negative dielectric anisotropy. The suspension was prepared by dispersing and stabilizing barium hexaferrite nanoplatelets in the nematic liquid crystal. The suspension exhibits superior magnetocapacitance and magnetoviscous effects compared with conventional isotropic ferrofluids. We show that electric and magnetic fields applied simultaneously perpendicular to the director have competing effects on the director’s alignment and the nanoplatelets’ magnetic moments. This ferromagnetic nematic suspension broadens the scope of fundamental studies and has the potential for applications in magnetoelectric and magneto-optic sensors.

Tellurium ($\mathrm{Te}$) is a two-dimensional semiconducting material with significant potential for tunable device applications. Here, we perform optical transmission measurements on a $\mathrm{Te}$-based field-effect transistor (FET) and reveal three major optical changes induced by electrical gating. (i) Intraband transition in $\mathrm{Te}$ evolves from localized Drude-Smith states to delocalized, standard Drude states as the hole carrier density increases. (ii) Interband transition and defect-level transition both shift to higher energies at distinct rates. (iii) The optical phonon peak of the ${\mathrm{Si}\mathrm{O}}_2$ dielectric layer undergoes a subtle yet distinct shift. We calculate the variation of dc dielectric constant $\epsilon (0)$ of ${\mathrm{Si}\mathrm{O}}_2$ induced by the optical phonon shift and support that the FET operates in practice within the linear charge response regime.

Recent studies in orbitronics have found large current-induced torques originating—in the current understanding—from incident orbital currents. These can be generated by the orbital Rashba-Edelstein effect (OREE) produced at the interface between some light metals and their oxide films, e.g., by a naturally oxidized copper layer (${\mathrm{Cu}}^{\ast }$). In the present work, using second-harmonic Hall techniques, we determine the ratio of orbital vs spin currents exerting torques on thin transition-metal $\mathrm{Co}$ ferromagnets in systems using an orbit-to-spin $\mathrm{Pt}$ converter as an interlayer with ${\mathrm{Cu}}^{\ast }$. Our results quantifying damping-like torques show that both orbital and spin contributions are enhanced in these systems. Moreover, the experimental determination of the decoherence length in a sample series with varying $\mathrm{Co}$ thickness clearly demonstrates the interfacial generation of the orbital currents in ${\mathrm{Cu}}^{\ast }$ by the OREE, leading to subsequent magnetic torque in $\mathrm{Co}$ over a typical length scale of several nanometers.