Magnetization evolution due to translational motion of spins in magnetic fields is governed by the Bloch-Torrey equations. In confined geometries, magnetization of such systems is often expressed as a series of eigenstates, the eigenvalues of which are related to the characteristic confinement length. We highlight the importance of nonground eigenvalues and their contribution to the relaxation of initially homogeneous magnetization by longitudinal and transverse ${}^1\mathrm{H}$ relaxation processes in porous materials. We show that a simple magnetic resonance relaxation measurement can reliably characterize confinement size in fluid-occupied porous materials. Pore sizes calculated from the eigenvalues are shown to agree with independent x-ray microtomography and electron microscopy measurements in rock samples.

We present a detailed analysis of the propagation of high-energy electron beams that have different shapes in a crystal of [100]-oriented zincblende GaN. Our study primarily focuses on Bessel beams and makes use of reformulated Bloch wave and multislice simulations. As a result of the simplicity of the momentum spectrum of a Bessel beam and the symmetry of the crystal, its propagation in the material can be described in a free-space representation, providing a deeper understanding of channeling phenomena and of probe intensity oscillation in the propagation direction. We also consider aperture-limited and Gaussian beams. The latter probes are shown to be optimal for coupling to 1s Bloch states and achieving minimal spreading along atomic columns.

Waveguides consisting of artificial media based on periodic structures at the subwavelength scale are a major open topic in contemporary applied physics and engineering. Recent research efforts focus on the properties of guided modes in artificial structures. However, as the cornerstone of applications, matching techniques between these interesting waveguides and traditional waveguides deserve more attention. We report a broadband adiabatic mode-matching technique for efficient coupling between conventional microwave transmission lines (a coplanar waveguide and a slotline) and one-dimensional (1D) interface waveguides consisting of transverse-electric (TE) and transverse-magnetic (TM) artificial impedance surfaces. The transverse electromagnetic (TEM) mode is adiabatically transformed to the line wave mode at the 1D impedance-interface. Proposed matching techniques open up avenues for applications of various impedance-interface waveguides.

We report the observation of antiferromagnetic insulator-mediated spin-orbit-torque switching in $\mathrm{Pt}/\mathrm{Ni}\mathrm{O}/{\mathrm{Co}}_{1-x}{\mathrm{Tb}}_x$ heterostructures. By measuring the current-induced shift in the magnetic hysteresis loops and the second-harmonic anomalous Hall resistance, we quantitatively determine the spin-orbit-torque efficiency in $\mathrm{Pt}/\mathrm{Ni}\mathrm{O}/{\mathrm{Co}}_{1-x}{\mathrm{Tb}}_x$ samples with different $\mathrm{Ni}\mathrm{O}$ thicknesses, uncovering a systematic evolution of the magnetic switching behavior. The measured spin-orbit-torque efficiency is enhanced in the low $\mathrm{Ni}\mathrm{O}$ thickness regime (1–2 nm), highlighting the efficient spin manipulation across a disordered antiferromagnetic insulator.

Adiabatic quantum-flux-parametron (AQFP) logic is an energy-efficient superconductor logic family; the energy dissipation of an AQFP gate can be arbitrarily reduced through adiabatic switching. In addition to high energy efficiency, AQFP logic has the advantage that it can easily introduce stochastic processes by exploiting naturally occurring thermal fluctuations. We propose using AQFP logic to implement an amoeba-inspired problem solver (APS), which is a stochastic local search method to explore solutions to combinatorial optimization problems such as the Boolean satisfiability problem (SAT). We designed a superconductor amoeba-inspired problem solver (SAPS) using AQFP logic, which finds solutions to a simple logical constraint satisfaction problem in the manner of APS, and fabricate it using a Nb integrated circuit fabrication process. Experimental results show that the probability distribution of the stochastic processes in AQFP logic can be controlled by the magnitude of bias current and that SAPS finds solutions using a small number of iterations when a moderate bias current is applied. The present results indicate the possibility of using AQFP logic to build hardware dedicated to the implementation of stochastic local search algorithms to solve combinatorial optimization problems such as SAT.

Laser gains, provided by either stimulated emissions, stimulated scatterings, or nonlinear frequency conversion, exclusively refer to the process in which pump waves transfer their energies to the emitted light. In these cases, the laser field could never acquire gain at the expense of the energy dissipation of itself. We introduce self-parametric amplification, a conceptually different gain mechanism for ultrafast fiber lasers. A prototype ultrafast fiber laser of this kind is realized by combining a standard linear gain with a nonlinear self-parametric gain that supports energy transfer from the spectral tails to the spectral center within the laser field. Remarkably, the ultrafast fiber laser outputs three coexisting dissipative solitons that periodically switch over consecutive round trips with quite different spectra. Our work provides a self-action gain mechanism conducive to developing advanced lasers and could shed light on the Fermi–Pasta–Ulam paradox and breathing soliton dynamics.

We report experimental and theoretical results on the lateral wet oxidation of bidimensional thin aluminum-rich layers into AlOx. We introduce a reaction-diffusion model of oxidation front propagation that includes effects of anisotropies and compare it to experimental results. This model can be used with any starting geometry, possibly nonconvex, and is deduced from the chemical reactions of wet oxidation of ${\mathrm{Al}}_{\mathrm{x}}{\mathrm{Ga}}_{1-\mathrm{x}}\mathrm{As}$ -based layers. Numerical simulations performed with simple and complex geometries are in excellent agreement with the experimental observations. Our method is general and can apply to other oxides. It opens the way to the fine control of wet-oxidation fronts and to the formation of AlOx layers with a desired geometry that has numerous practical and relevant applications for, e.g., waveguiding or carrier confinement in photonics.

We report on the near-field imaging of atomically thin layers of two-dimensional (2D) materials using photoinduced force mapping. This is accomplished by modifying a traditional atomic force microscopy set up to detect optical forces between a nanoscale tip and a photoexcited sample. Our set up facilitates the imaging of few-layer flakes of ${\mathrm{Mo}\mathrm{S}}_2$ or ${\mathrm{WS}}_2$ and the simultaneous acquisition of optical force spectra, both in ambient and vacuum conditions. The evaluated force spectra in both samples exhibit the characteristic excitonic resonance peaks that are most typically observed in far-field absorption spectroscopy. We also show that nanoscale defect sites and flake edges can be distinguished from the crystalline surfaces with a high spectral resolution. Our results pave the way toward gaining a wholesome understanding of optical interactions and structure-property correlations in 2D materials and their heterostructures.

Magnonic circuit elements generally operate using signals that are either amplitude or phase modulated. We propose a simple all-magnon circuit element capable of converting between these two types of encoding, and support our design with simulations. We highlight the potential of our technique to augment existing devices and propose an alternative schematic for an “equality” gate and exclusive nor gate.

Artificial micro- and nanomachines are of great interest to both scientific and engineering societies. We investigate an alternative actuation mechanism using locally enhanced microstreaming in a low-frequency acoustic field and propose a controllable high-speed acoustic rotary microsystem. With numerical simulations, we show that the local acoustic streaming field can be enhanced when utilizing the low-frequency vibration from the micropillar structure. In particular, the elliptical oscillation from the micropillar occurs at hundreds of kilohertz and gives rise to the reinforced rotary microstreaming, thereby enabling the high-speed rotation of microparticles. Using this facile and controllable methodology, a polystyrene (PS) microrotor with a diameter of 10 µm can be driven to rotate at a fast speed of up to 5000 rpm. This actuation mechanism along with the favorable acoustic rotary microsystem provides another alternative for designing high-speed rotary micromachines.

Strong magnetic field gradients can produce a synthetic spin-orbit interaction that allows high-fidelity electrical control of single electron spins. We investigate how a field gradient impacts the spin relaxation time $T_1$ by measuring $T_1$ as a function of the magnetic field $B$ in silicon. The interplay of charge noise, magnetic field gradients, phonons, and conduction-band valleys leads to a maximum relaxation time of $160\mathrm{ms}$ at low fields, a strong spin-valley relaxation hotspot at intermediate fields, and a $B^4$ scaling at high fields. $T_1$ is found to decrease with increasing lattice temperature as well as with added electrical noise. In comparison, samples without micromagnets have a significantly greater $T_1$.

We describe a phase-coherent multifrequency lock-in measurement technique that uses the inverse Fourier transform to reconstruct the nonlinear current-voltage characteristic of a nanoscale junction. The method provides separation of the galvanic and displacement currents in the junction and easy cancellation of the parasitic displacement current from the measurement leads. These two features allow us to overcome traditional limitations imposed by the low conductance of the junction and the high capacitance of the leads, thus providing an increase in measurement speed of several orders of magnitude. We demonstrate the method in the context of conductive atomic force microscopy, acquiring current-voltage characteristics at every pixel while scanning at standard imaging speed.

Dispersive sensing is a powerful technique that enables scalable and high-fidelity readout of solid-state quantum bits. In particular, gate-based dispersive sensing has been proposed as the readout mechanism for future topological qubits, which can be measured by single electrons tunneling through zero-energy modes. The development of such a readout requires resolving the coherent charge tunneling amplitude from a quantum dot in a Majorana-zero-mode host system faithfully on short time scales. Here, we demonstrate rapid single-shot detection of a coherent single-electron tunneling amplitude between $\mathrm{In}\mathrm{As}$ nanowire quantum dots. We realize a sensitive dispersive detection circuit by connecting a sub-GHz, lumped-element microwave resonator to a high-lever arm gate on one of the dots. The resulting large dot-resonator coupling leads to an observed dispersive shift that is of the order of the resonator linewidth at charge degeneracy. This shift enables us to differentiate between Coulomb blockade and resonance—corresponding to the scenarios expected for qubit-state readout—with a signal-to-noise ratio exceeding 2 for an integration time of $1\mu \mathrm{s}$. Our result paves the way for single-shot measurements of fermion parity on microsecond time scales in topological qubits.

We report a tunable spin-mixing conductance, up to $\pm 22\mathrm{\%}$, in a ${\mathrm{Y}}_3{\mathrm{Fe}}_5{\mathrm{O}}_{12}/$platinum (YIG/$\mathrm{Pt}$) bilayer. This control is achieved by applying a gate voltage with an ionic-gate technique, which exhibits a gate-dependent ferromagnetic resonance line width. Furthermore, we observe a gate-dependent spin pumping and spin Hall angle in the $\mathrm{Pt}$ layer, which is also tunable up to $\pm 13.6\mathrm{\%}$. This work experimentally demonstrates spin-current control through spin pumping and a gate voltage in a YIG/$\mathrm{Pt}$ bilayer, demonstrating the crucial role of the interfacial charge density for the spin-transport properties in magnetic-insulator–heavy-metal bilayers.

A liquid marble, a liquid droplet coated with hydrophobic powder, is an emerging digital microfluidic platform. It can potentially serve as a mixer or reactor for chemical and biological assays in the microscale. Automated manipulation of liquid marbles is essential for the implementation of more microfluidic functions in the technology platform of “lab in a marble”. We report the analytical and experimental results of trapping a floating liquid marble using dielectrophoresis in a nonuniform electric field. Liquid marbles with volumes ranging from 5 to $50\mu \mathrm{L}$ are effectively trapped by the dielectrophoretic force from a horizontal distance ranging from 10 to 60 $\mathrm{mm}$ and under an applied voltage ranging from 1.6 to 5 $\mathrm{kV}$. A one-dimensional analytical model is then proposed for the trapping process and agrees well with experimental data. Finally, based on the relationship between the static friction coefficient and the Bond number of a floating liquid marble, an operation map is derived for successful trapping of the liquid marble, providing a better insight into controlled manipulation of liquid marbles.

Accurate microscopic description of the charge-trapping process from semiconductor to defects in the dielectric-oxide layer is of paramount importance for understanding many microelectronic devices such as complementary metal-oxide-semiconductor (CMOS) transistors, as well as electrochemical reactions. Unfortunately, most current microscopic descriptions of such processes are based on empirical models with parameters fitted to experimental device performance results or simplified approximations like the Wentzel-Kramers-Brillouin (WKB) method. Some critical questions are still unanswered, including: What controls the charge-hopping rate, the coupling strength between the defect level to semiconductor level, or the energy difference? How does the hopping rate decay with defect-semiconductor distance? What is the fluctuation of the defect level, especially in amorphous dielectrics? Many of these questions can be answered by ab initio calculations. However, to date, there are few ab initio studies for this problem mainly due to technical challenges from atomic-structure construction to large-system calculations. Here, using the latest advances in calculation methods and codes, we study the carrier-trapping problem using density-functional theory (DFT) based on the Heyd-Scuseria-Ernzerhof (HSE) exchange correlation functional. The valence bond random-switching method is used to construct the crystalline-$\mathrm{Si}$–amorphous-${\mathrm{Si}\mathrm{O}}_2$ ($c\text{−}\mathrm{Si}/a\text{−}{\mathrm{Si}\mathrm{O}}_2$) interfacial atomic structure, and the HSE yields a band offset that agrees well with experiments. The hopping rate is calculated with the Marcus theory, and the hopping-rate dependences on the gate potential and defect distances are revealed, as well as the range of fluctuation results from amorphous structural variation. We also analyze the result with the simple WKB model and find a major difference in the description of the coupling constant decay with the defect-semiconductor distance. Our results provide the ab initio simulation insights for this important carrier-trapping process for device operation.

In this work, we propose the use of contact resonances, controlled via an external magnetic field, as a tunable platform to manipulate the dispersion of surface acoustic waves (SAWs). We exploit the analogy between surface acoustic waves in a semi-infinite medium and edge waves in a plate, to realize a compact experimental setup and to demonstrate our tuning strategy. The setup consists of a set of ferromagnetic bead resonators in contact with thin, permanent magnets and positioned at the free edge of an elastic plate. An additional set of magnets, placed at a controlled and variable distance from the beads, is used to alter the contact stiffness and natural frequencies of the bead resonators. We exploit resonances to open large-frequency band gaps via edge-wave hybridization and implement our tuning strategy to shift their frequency ranges. We predict the tuned dispersive properties of hybridized edge waves via numerical models and experimentally reconstruct them via laser vibrometry, finding excellent agreement. The use of magnetic interaction and contact mechanics as a tuning strategy for SAW systems could pave the way toward programmable devices for sensing and electronic components.

The drastic difference between complex transmission coefficients for ${\mathrm{TE}}_{11}$ and ${\mathrm{TH}}_{11}$ GHz modes propagating through subwavelength gradient barriers in a metallic waveguide is examined. Amplitude-phase structures of the transmitted ${\mathrm{TE}}_{11}$ and ${\mathrm{TH}}_{11}$ modes are described in the framework of an exactly solvable model of these barriers. A sharp contrast in transmission is found between degenerate ${\mathrm{TE}}_{11}$ and ${\mathrm{TH}}_{11}$ modes distinguished by their polarization structures due to polarization-dependent tunneling and nonlocal energy transport through thin gradient dielectric barriers.

In recent years different setups based on external cavities have been developed, in order to enhance the performance of pulsed semiconductor mode-locked lasers, namely the peak power and width of the emitted pulses. Depending on the operating conditions and the cavity configuration, pulse cluster solutions emerge with a nonidentical temporal interpulse spacing, which limit the performance of such devices. In this work we present a system of multidelay differential equations to describe the dynamics of a passively mode-locked vertical-external-cavity surface-emitting laser with V-shaped cavity geometry, that allows for an effective modeling and detailed studies of parameter dependencies. We apply numeric integration as well as path-continuation methods to understand the underlying bifurcation scenarios and hence the parameter regions of stable operation. Our investigations indicate that pulse cluster solutions emerge along the fundamental periodic solution branch with a critical influence of the cavity round-trip time on the number of pulses in the cluster. We find regions of multistability of higher-order pulse clusters and predict how different types of dynamics can be favored by tuning the cavity geometry.

Recently, metamaterials-inspired diffraction gratings (or metagratings) have demonstrated unprecedented efficiency in wavefront manipulation by means of relatively simple structures. Conventional one-dimensional (1D) gratings have a profile modulation in one direction and a translation symmetry in the other. In 1D metagratings, the translation invariant direction is engineered at a subwavelength scale, which allows one to accurately control polarization line currents and, consequently, the scattering pattern. In bright contrast to metasurfaces, metagratings cannot be described by means of surface impedances (or local reflection and transmission coefficients). In this paper, we present a simulation-based design approach to construct metagratings in the “unit cell by unit cell” manner. It represents an analog of the local periodic approximation that has been used to design space-modulated metasurfaces and allows one to overcome the limitations of straightforward numerical optimization and semianalytical procedures that have been used to date to design metagratings. Electric and magnetic metagrating structures responding to, respectively, transverse electric and transverse magnetic incident plane waves are presented to validate the proposed design approach.