We experimentally study the current-induced effective spin-orbit torque (SOT) efficiency and the spectral characteristics of current-driven coherent magnetic dynamics in spin Hall nano-oscillators (SHNOs) based on the $\mathrm{Pt}$/$\mathrm{Ni}$/Py trilayer. We determine that the $\mathrm{Pt}$/$\mathrm{Ni}$/Py trilayer structure has an effective dampinglike torque efficiency ${\xi }_{\mathrm{DL}}\sim 0.055$, comparable with the $\mathrm{Pt}$/$\mathrm{Co}$ and $\mathrm{Pt}$/$\mathrm{Fe}$ bilayer systems with a strong interfacial spin-orbit coupling and magnetic proximity effect. Furthermore, the microwave-generation spectra show that the $\mathrm{Pt}$/$\mathrm{Ni}$/Py-based SHNOs exhibit a single nonlinear self-localized bullet mode with a frequency below $f_{\mathrm{FMR}}$ and a significant current-dependent frequency red shift due to its strong nonlinear effect, which is very similar to that in $\mathrm{Pt}$/Py-based SHNOs, at low oblique angles $\phi \le {50}^{\circ }$. In contrast, at high oblique angles $\phi \ge {55}^{\circ }$, the spectra show two oscillating peaks with very similar field-, current-, and temperature-dependent behaviors, which suggests the spatial coexistence of two same-type nonlinear self-localized bullet modes at certain currents and magnetic fields. Additionally, the observed linear temperature dependence of the minimum line width, which resembles the thermal broadening of single-mode oscillation, further confirms that two localized bullet modes are independent, spatially separated, and lack thermally activated mode-transition behavior. Our results provide valuable information for the electronic control of coherent magnetic dynamics by combining bulk and interfacial spin-orbit coupling effects in the magnetic heterostructures.

We study the capabilities of time-modulated diffraction gratings as imaging devices. It is shown that a time-dependent but transversally homogeneous slab can be used to make a perfect image of an object in the far-field, since all the evanescent modes couple to propagative time-diffracted orders. It is found that, if the image to be obtained is axially symmetric, it can be recovered by measuring the time signal at a single point, without the need to perform a spatial scan, so that time gratings can act as well as single-pixel imaging devices. In the case of having an object without axial symmetry, the time grating can be combined with a spatial grating, and then the full image can be recovered again with a measurement at a single point. We apply the theory of compressive sensing to optimize the recovery method, and numerical examples are provided. We show, therefore, that time-modulated gratings can be used to perfectly recover the image of an object in the far-field and after measuring at a single point in space, making them a promising approach to superresolution and ultrafast imaging.

The theory and practical realization of a broadband quantum-noise generator based on an original integrated optical beam splitter in the form of a Mach-Zehnder interferometer is demonstrated. The beam splitter with a double output, made on a lithium niobate substrate, provides accurate electro-optical balancing of the homodyne quantum-noise detection circuit. The experimentally obtained excess of quantum noise over classical noise is 12 dB in the frequency band over 4 GHz, which is the best parameters of quantum-noise generators known from the literature.

We study magnetotransport in heterostructures composed of the van der Waals antiferromagnet ${\mathrm{Cr}\mathrm{PS}}_4$ and the heavy metals $\mathrm{Pt}$ and $\mathrm{Pd}$. In both types of devices, the transverse resistance ($R_{xy}$) signal reveals the spin-flop transition of ${\mathrm{Cr}\mathrm{PS}}_4$ and a strong anomalous Hall effect at temperatures up to 300 K. While ${\mathrm{Cr}\mathrm{PS}}_4/\mathrm{Pt}$ devices allow for easy detection of the spin-flop transition, ${\mathrm{Cr}\mathrm{PS}}_4/\mathrm{Pd}$ devices show a more substantial enhancement in anomalous Hall effect at temperatures above 70 K and exhibit a topological Hall effect signal, possibly related to chiral spin structures at the interface. The longitudinal magnetoresistance ($R_{xx}$) results from a combination of spin-Hall magnetoresistance and the negative magnetoresistance that can be explained by a field-induced change of the electronic band structure of ${\mathrm{Cr}\mathrm{PS}}_4$.

Local current-voltage characteristics for low-dimensional transition-metal dichalcogenides (LDTMD), as well as the reconstruction of their local density of states (LDOS) from scanning tunneling microscopy (STM) experiments, are of fundamental interest and can be useful for advanced applications. Most of the existing models either have limited applicability for complex-shaped LDTMDs (e.g., those based on the Simmons approach) or require solving of an ill-defined integral equation to deconvolute the unknown LDOS (e.g., those based on the Tersoff approach). Using a serial expansion of the Tersoff formulas, we propose a flexible method to reconstruct the LDOS from local current-voltage characteristics measured in STM experiments. We establish a set of key physical parameters, which characterize the tunneling current of a STM-probe–sample contact and the sample LDOS expanded in Gaussian functions. Using a direct variational method coupled with probabilistic analysis, we determine these parameters from the STM experiments for ${\mathrm{MoS}}_2$ nanoflakes with different numbers of layers. The main result is the reconstruction of the LDOS in a relatively wide energy range around the Fermi level, which allows us to gain insight into the local band structure of LDTMDs. The reconstructed LDOS reveal pronounced size effects for the single-layer, two-layer, and three-layer ${\mathrm{MoS}}_2$ nanoflakes, which we relate to the low dimensionality and strong bending or corrugation of the nanoflakes. We hope that the proposed elaboration of the Tersoff approach, allowing LDOS reconstruction, will be of critical interest for the quantitative description of STM experiments and also of use to better understand the microscopic physical aspects of the surface, strain, and bending contributions to the LDTMDs’ electronic properties.

Regardless of the significant progress in photodetectors (PDs), most conventional technologies are equipped with optical filters for spectral discrimination, which results in expensive circuitry as well as a high incidence of energy loss. Different from traditional PDs, a ${\mathrm{Mo}\mathrm{S}}_2/\mathrm{Zn}\mathrm{O}$ heterostructure-based PD is demonstrated that exhibits a bias-dependent switchable spectral response. A low-band-gap ${\mathrm{Mo}\mathrm{S}}_2$ thin film is vertically stacked on top of a high-band-gap $\mathrm{Zn}\mathrm{O}$ film that allows selective charge transport from each layer by modulating the applied bias, resulting in a fine discrimination between visible and near-infrared (NIR) light. Under a lower applied bias, a dominant photoresponse in the visible region by the $\mathrm{Zn}\mathrm{O}$ film is observed, whereas an enhanced response in the NIR region is obtained at higher bias, which is attributed to the generation of charge carriers in the ${\mathrm{Mo}\mathrm{S}}_2$ region. The excellent figures of merit obtained in the study attest to the high quality of the device, paving the way for fabricating energy-efficient imaging systems free of optical filters.

Magnetic skyrmions are promising candidates as elementary nanoscale bits in logic-in-memory devices, intrinsically merging high-density memory and computing capabilities. Here we exploit the dynamics of skyrmions interacting with anisotropy energy barriers patterned by ion irradiation to design programmable logic gates. Using micromagnetic simulations with experimental parameters, we show that a fine tuning of the barrier height and width allows the selective tunneling of skyrmions between parallel nanotracks triggered by skyrmion-skyrmion interaction. This can be leveraged to design a skyrmion demultiplexer logic gate that works solely using skyrmions as logic inputs. By cascading and connecting demultiplexer gates with a specific topology, we develop a fully programmable logic gate capable of producing any possible logic output as a sum of all minterms generated by a given set of inputs without requiring any complex additional electric or magnetic interconversion. The proposed design is fully conservative and cascadable, enabling purely skyrmion-based logic-in-memory devices.

Lethal cardiac arrhythmias often involve the occurrence of spiral waves, whose control is essential for the treatment of the disease. While high-voltage shock-based control methods rely on ensuring an abrupt electrical synchronization of the heart, low-energy techniques mostly cause drift-induced termination of these waves. In particular, such a drift can be induced by a spatiotemporal modulation of domain excitability in optogenetically modified cardiac tissue. Here we demonstrate a low-energy optogenetics-based approach to suppress spiral waves via their transient chaotization and rapid drift.

We study arrays of planar $\mathrm{Nb}$ Josephson junctions with contacts to intermediate electrodes, which allow measurements of individual junctions and, thus, provide an insight into intricate array dynamics. We observe strong indications for array phase locking, despite a significant interjunction separation. Several unusual phenomena are reported, such as a bistable critical current with reentrant superconductivity upon switching of nearby junctions; and “incorrect” Shapiro steps, occurring at mixing frequencies between the external rf radiation and the internal Josephson frequency in nearby junctions. Our results reveal a surprisingly strong and long-range interjunction interaction, which is attributed to nonlocality of planar-junction electrodynamics, caused by the long-range spreading of stray electromagnetic fields. The nonlocality greatly enhances the high-frequency interjunction coupling and enables large-scale synchronization. Therefore, we conclude that planar geometry is advantageous for the realization of coherent Josephson electronics.

Spin relaxometry with nitrogen-vacancy (N-$V$) centers in diamond offers a spectrally selective, atomically localized, and calibrated measurement of microwave-frequency magnetic noise, presenting a versatile probe for condensed-matter and biological systems. Typically, relaxation rates are estimated with curve-fitting techniques that do not provide optimal sensitivity, often leading to long acquisition times that are particularly detrimental in systems prone to drift or other dynamics of interest. Here we show that adaptive Bayesian estimation is well suited to this problem, producing dynamic relaxometry pulse sequences that rapidly find an optimal operating regime. In many situations (including the system we employ), this approach can speed the acquisition by an order of magnitude. We also present a four-signal measurement protocol that is robust to drifts in spin readout contrast, polarization, and microwave pulse fidelity while still achieving near-optimal sensitivity. The combined technique offers a practical, hardware-agnostic approach for a wide range of N-$V$ relaxometry applications.

We study the physics of a magnetic molecule described by a “giant” spin with multiple ($d>2$) spin states interacting with the quantized cavity field produced by a superconducting resonator. By means of the input-output formalism, we derive an expression for the output modes in the dispersive regime of operation. It includes the effect of magnetic anisotropy, which makes different spin transitions addressable. We find that the measurement of the cavity transmission allows us to uniquely determine the spin state of the qudits. We discuss, from an effective Hamiltonian perspective, the conditions under which the qudit readout is a nondemolition measurement and consider possible experimental protocols to perform it. Finally, we illustrate our results with simulations performed for realistic models of existing magnetic molecules.

The quantum Hall system possesses topologically protected edge states, which have enormous theoretical and practical implications in both fermionic and bosonic systems. Harnessing the quantum Hall effect in optical platforms with lower dimensionality is highly desirable with synthetic dimensions and has attracted broad interests in the photonics society. Here, we introduce an alternative way to realize the artificial magnetic field in a frequency dimension, which is achieved in a pump-probe configuration with cross-phase modulations in a one-dimensional four-waveguide array. The dynamics of the topological chiral edge state has been studied and the influence from the crosstalk of the pump fields has been explored. Our work shows an all-optical way to simulate the quantum Hall system in a photonic system and holds potential applications in manipulating light in waveguide systems.

We demonstrate, numerically, the possibility of manipulating the spin states of molecular nanomagnets with shaped microwave pulses designed with quantum optimal control theory techniques. The state-to-state or full gate transformations can be performed in this way in shorter times than using simple monochromatic resonant pulses. This enhancement in the operation rates can therefore mitigate the effect of decoherence. The optimization protocols and their potential for practical implementations are illustrated by simulations performed for a simple molecular cluster hosting a single ${\mathrm{Gd}}^{3+}$ ion. Its eight accessible levels (corresponding to a total spin $S=7/2$) allow encoding an eight-level qudit or a system of three coupled qubits. All necessary gates required for universal operation can be obtained with optimal pulses using the intrinsic couplings present in this system. The application of optimal control techniques can facilitate the implementation of quantum technologies based on molecular spin qudits.

Getting wireless signals around obstacles or passing them through walls is proven to be challenging for electromagnetic waves with a short wavelength and some energy-efficient buildings due to thick insulating materials. Here, we propose a scheme of through-wall wireless communication by applying purposely designed passive metalenses for an asymmetric background medium of the wall. An ultrathin metalens consisting of three layers of metallic patterns is applied to focus the incoming waves to the other side of the wall with high efficiency. The focusing effect is verified by scanning the spatial distribution of electric fields. Due to the focusing effect, the wireless signal strength is significantly enhanced while propagating through the wall. To validate its use in the 5-GHz Wi-Fi environment, we demonstrate that the metalens can reconnect a network channel that is otherwise broken due to weak signal strength, and thus, significantly increase the data transmission rate. Our work opens an unobstructive and retrofitting approach for sustaining wireless communication in future eco-friendly buildings beyond 5G and 6G.

Surface-acoustic-wave (SAW) sensors have undergone outstanding developments during the last decades. However, for biosensing applications, they struggle to compete with optical sensing technologies. In this work, we present a Love-wave-based sensing platform that leverages the use of the local resonances of micropillars fabricated on the surface of the guiding layer. We demonstrate numerically and experimentally that the Love-wave interaction with the micropillars produces sharp attenuation dips in the transmission spectrum. These dips are associated with the excitations of flexural and torsional resonance modes of the pillars. We utilize these modes to achieve higher detection sensitivity of temperature variation and mass loading using sugar and microbeads concentrations in aqueous solutions. Integrating a lattice of micropillars into SAW-based devices offers a strong potential for detecting low particles concentrations.