Chiral halide perovskites are being extensively studied due to their promising spintronic and optoelectronic properties, where the organic chiral ligands introduce chirality into halide perovskites. Right-handed and left-handed chiral materials are mirror images of one another and break the inversion symmetry, which produces ferroelectricity. In this work, we study the dielectric, piezoelectric, and ferroelectric properties of (R)-(−)-1-cyclohexylethylammonium)${\mathrm{Pb}\mathrm{I}}_3$ (R-CYHEA${\mathrm{Pb}\mathrm{I}}_3$), a chiral, one-dimensional perovskite. We performed and analyzed complex impedance spectroscopy; ac conductivity; and the complex electric modulus using the Maxwell-Wagner equivalent circuit model, the universal power law, the Havrilliak-Negami (HN) model, and the Kohlrausch-Williams-Watts (KWW) model to understand the transport and relaxation mechanism in the chiral R-CYHEA${\mathrm{Pb}\mathrm{I}}_3$ perovskite over wide temperature (313–473 K) and frequency (4 Hz–8 MHz) ranges. The dc conductivity is almost constant in the paraelectric-to-ferroelectric phase-transition region (PTR) but increases below and above this region. The activation energy of this region is very low, about 0.09 eV, while below the PTR, the activation energy is about 0.85 eV, and above the PTR, it is about 0.90 eV. We further note that the conduction mechanism changes from overlapped large polaron tunneling to correlated barrier hopping due to the ferroelectric-to-paraelectric phase transition. The activation energy derived from the relaxation time (using HN and KWW models) agrees with that obtained from the dc conductivity. In addition, we measured the saturation polarization of 0.01 µC/${\mathrm{cm}}^2$ at a 4-kV/cm applied electric field and a piezoelectric constant ($d_{33}$) of about 36 pm/V at the maximum applied bias voltage of 10 V. Finally, we fabricated a polyvinylidene fluoride and 3-wt % R-CYHEA${\mathrm{Pb}\mathrm{I}}_3$ chiral perovskite composite film for the development of high-performance energy-harvesting nanogenerators.

By combining the phenomena of voltage-controlled magnetic anisotropy (VCMA) and chiral resonant scattering of spin waves, we demonstrate through micromagnetic simulations that it is possible, by applying a dc voltage, to achieve tunable attenuation of spin waves propagating in an yttrium iron garnet (YIG) film. The resultant device, dubbed as an electrical chiral magnonic resonator (ECMR), provides a solution for implementing the synapse function in a spin-wave-based neuromorphic computational system, which demands that the weight factor be continuously changeable. The voltage-based mechanism ensures the advantages of minimal energy consumption and physical compactness when compared with other tuning strategies, such as a local Oersted field generated by passing current through electrical leads. On the other hand, by applying a rf voltage, it is possible to utilize the same ECMR device design to achieve parametric amplification of spin waves in the same YIG film. This provides a viable solution to apply the concept of voltage-based parametric amplification to YIG materials. An analytical model is developed to describe the scattering characteristics of the ECMR amplifier, which enable fast computation in the case of magnonic circuitry design involving a large number of amplifier devices.

We investigate the effect of coherence on the energy transfer between a donor and an acceptor molecule located on opposite sides of a ${\mathrm{Mo}\mathrm{S}}_2$ nanodisk. We study the energy-transfer efficiency by considering each molecule as a two-level quantum system using the Lindblad master equation, in the limits of fast (within nanoseconds) and slow (within microseconds) free-space relaxation. We incorporate the influence of the ${\mathrm{Mo}\mathrm{S}}_2$ nanodisk via the electromagnetic Green’s-function approach and take into account the donor dissipation and the acceptor charge-separation rate. We compare the energy-transfer efficiency with and without quantum coherence, for various separation distances and dipole orientations of the donor and acceptor. We find that the presence of the ${\mathrm{Mo}\mathrm{S}}_2$ nanodisk enhances the donor and acceptor relaxation rate, as well as the coherent and the incoherent coupling between them. We also find high energy-transfer efficiency between the donor and acceptor in the presence of strong coherence, primarily at a small separation distance from the ${\mathrm{Mo}\mathrm{S}}_2$ nanodisk. Additionally, we observe ultrafast energy transfer in the presence of coherence, which is largely enhanced in comparison to the incoherent coupling, when the donor and acceptor transition energies are off resonant to the excitonic ${\mathrm{Mo}\mathrm{S}}_2$ resonances. These results are important for nanotechnology applications; in particular, the design of novel light-harvesting devices.

The connectivity of self-assembled networks of nanowires and nanoparticles is believed to strongly influence their performance in brainlike (neuromorphic) computing applications. Here we present a new perspective on the connectivity of these networks in which their neuronlike active elements are viewed in the same way as the nodes in artificial and biological neuronal networks. We consider two-dimensional and quasi-three-dimensional networks of nanowires and percolating networks of nanoparticles and show that, from this new perspective, they all have similar small-world characteristics. Other characteristics which may impact the computational performance of the networks are also investigated, including their assortativity and the scalefree nature of the nanoparticle networks. Taken together, these results allow comparison of key network characteristics for a variety of self-assembled nanoscale networks, and provide a basis for detailed investigations of computational performance.

Unlocking the full potential of wavefront manipulation and particle trapping with high spatial precision requires a flexible approach to remotely trigger the desired ultrasonic wave with high central frequency. In this work, we propose a scheme for generating ultrasonic vortices beyond 3 MHz through optoacoustic conversion with the tailored logarithmic spiral absorbing surface. By illuminating the light-absorbing surface with an 8-ns pulsed laser, the laser-generated ultrasonic waves from each loop of the spirals will coherently interfere with each other near their symmetric axis of propagation, and the vortex is then produced, with the common features of a helical wavefront and central null pressure. The generated vortex field with different topological charges is scanned in three dimensions with high spatial resolution using a parabolic focusing detection system. The proposed scheme can produce the desired vortex field at above 3.5 MHz without resorting to elaborate fabrication techniques or distributed arrays, and therefore, has potential in various fields, ranging from particle manipulation to other biomedical applications.

Individually trapped Rydberg atoms show significant promise as a platform for scalable quantum simulation and for the development of programmable quantum computers. In particular, the Rydberg-blockade effect can be used to facilitate both fast qubit-qubit interactions and long coherence times via low-lying electronic states encoding the physical qubits. To bring existing Rydberg-atom-based platforms a step closer to fault-tolerant quantum computation, we demonstrate high-fidelity state and circuit preparation in a system of five atoms. We specifically show that quantum control can be used to reliably generate fully connected cluster states and to simulate the error-correction encoding circuit based on the “Perfect Quantum Error Correcting Code” by Laflamme et al. [Phys. Rev. Lett. 77, 198 (1996)]. Our results make these ideas and their implementation directly accessible to experiments and demonstrate a promising level of noise tolerance with respect to experimental errors. With this approach, we motivate the application of quantum control in small subsystems in combination with the standard gate-based quantum circuits for direct and high-fidelity implementation of few-qubit modules.

Fluorescent nanodiamonds (FNDs) have been exploited as sensitive quantum probes for nanoscale chemical and biological sensing applications, with the majority of demonstrations to date relying on the detection of single FNDs containing either single nitrogen vacancies or nitrogen-vacancy ensembles. This places significant limits on the measurement time, throughput and statistical significance of a measured result as there is usually marked inhomogeneity within FND samples. Here, we have developed a measurement platform that can report the $T_1$ spin relaxation time from a large ensemble of FNDs in solution. We first describe a refined sensing protocol for this modality and then use it to identify the optimal FND size for the detection of paramagnetic targets. Our approach is simple to set up, robust and can be used for rapid material characterization for a variety of in-situ quantum sensing applications.

Using a fluxonium qubit with in situ tunability of its Josephson energy, we characterize its energy relaxation at different flux biases as well as different Josephson energy values. The relaxation rate at qubit energy values, ranging more than 1 order of magnitude around the thermal energy $k_{B}T$, can be quantitatively explained by a combination of dielectric loss and $1/f$ flux noise with a crossover point. The amplitude of the $1/f$ flux noise is consistent with that extracted from the qubit dephasing measurements at the flux sensitive points. In the dielectric loss dominant regime, the loss is consistent with that arising from the electric dipole interaction with two-level-system (TLS) defects. In particular, by increasing the Josephson energy, thus decreasing the qubit frequency at the flux insensitive spot, we find that the qubit exhibits increasingly weaker coupling to TLS defects, which is desirable for high-fidelity quantum operations. Our work establishes a generic noise model for the design of high coherence fluxonium and future generations of noise resilient superconducting qubits.

We investigate the effect of buffer gases on the coherent population trapping resonance induced by a $\sigma$-polarized optical field in ${}^{87}\mathrm{Rb}$ atoms. Our experimental results show that inert gases, which depolarize the excited state of alkali-metal atoms, provide higher contrast than nitrogen that effectively quenches their fluorescence. We also demonstrate that elimination of spontaneous radiation does not significantly decrease the width at moderate temperatures of an atomic medium. Therefore, a mixture of inert gases can be preferable over a mixture with nitrogen for atomic clocks.

Weyl semimetals are bulk solids in which chiral anomalies, i.e., negative magnetoelectric and magnetothermal resistances, exist as a result of the chiral properties of the Weyl fermions. The thermal chiral anomaly has potential in devices that actively control heat fluxes; these would be an early application of topological properties, realized after the materials are optimized. Here, we optimized the band structure of ${\mathrm{Bi}}_{1-x}{\mathrm{Sb}}_x$ alloys in the topological insulator phase and in their field-induced Weyl semimetal phases to maximize the thermal chiral anomaly by changing the $\mathrm{Sb}$ concentration and by doping ${\mathrm{Bi}}_{1-x}{\mathrm{Sb}}_x$ alloys either with n-type $\mathrm{Te}$ or with p-type $\mathrm{Sn}$. We show that the chiral anomalies are maximized when the chemical potential is at the Weyl points and that Weyl fermions are protected against scattering on phonons and neutral defects but not necessarily on charged particles like ionized impurities and electrons in trivial pockets. In our optimum material, around 30% of the total heat (carried by phonons, trivial electrons, and the chiral anomaly) is carried by the anomalous heat current (the chiral anomaly). The latter is highly switchable under a magnetic field. The maximum effect we observe is an anomalous thermal conductivity at 7 T that is 700% larger than the zero-field electronic thermal conductivity at T = 40 K in a x = 0.1 sample with p-type doping to 3.90 × ${10}^{15}{\mathrm{cm}}^{-3}$ with a mobility of $2350000{\mathrm{cm}}^2{V}^{-1}{\mathrm{s}}^{-1}$.

Asymmetric heat-transfer systems, often referred to as thermal diodes or thermal rectifiers, have garnered increasing interest due to their wide range of application possibilities. Most of those previous macroscopic asymmetric thermal devices either resort to nonlinear thermal conductivities with strong temperature dependence that may be quite limited by or fixed in natural materials or rely on active modulation that necessitates auxiliary energy payloads. Here, we establish a straightforward strategy of passively realizing asymmetric heat transfer with linear conductive materials. The strategy also introduces an interrogative perspective into the previous design of passive asymmetric heat transfer utilizing nonlinear thermal conductivity, correcting the misconception that thermal rectification is impossible with separable nonlinear thermal conductivity. The nonlinear-perturbation mode can be versatilely engineered to produce an effective and wide-ranging perturbation in heat conduction, which imitates and bypasses intrinsic thermal nonlinearity constraints set by naturally occurring counterparts. Independent experimental characterizations of surface thermal radiation and thermal convection verify that heat exchange between a graded linear thermal metamaterial and the ambient surroundings can be tailored to achieve macroscopic asymmetric heat transfer. Our work is envisaged to inspire conceptual models for heat-transfer control, serving as a robust and convenient platform for advanced thermal management and thermal computation.

Dirac cone formation and a method for dynamically controlling the band gap using double-layer ring dipole arrays (RDAs) are demonstrated and proposed. The design is mainly based on the composite right-handed–left-handed circuit theorem. It is theoretically and analytically confirmed that the Dirac cone appears at the optimum separation in double-layer RDAs, which are known to have surface-wave modes in the case of a single-layer RDA. It is also found that the band gap can be formed and controlled by decreasing the separation between the two layers. The Dirac cone formation and its dynamic control method on the artificial structure will open the possibility of new transistor applications as an artificial electronic material showing the properties of Dirac half-metals.

We demonstrate single-photon emission in strongly confined piezoelectric (211)B $\mathrm{In}\mathrm{As}/\mathrm{Ga}\mathrm{As}$ quantum dots at an elevated temperature of 230 K, exploiting the enhanced exciton-biexciton splittings in the system. This is a high temperature allowing for noncryogenic operation of a single-photon emitter based on III-arsenide quantum dots. A determining factor toward this result is the incorporation of the quantum dot layer in between $\mathrm{Ga}\mathrm{As}/\mathrm{Al}\mathrm{As}$ short-period superlattices, improving drastically the carrier confinement and temperature stability of the dot emission, allowing the observation of distinct exciton and biexciton emission peaks up to 260 K and single-photon emission at a high temperature.

Multifunctional tunnel junction is a kind of electronic device and the emergence of van der Waals (vdW) materials provides a promising opportunity for the development of multifunctional tunnel junctions and the miniaturization of electronic devices beyond Moore’s law. Here, we propose a symmetric vdW antiferroelectric multiferroic tunnel junction (AFMFTJ) based on ${\mathrm{Fe}}_3{\mathrm{Ge}\mathrm{Te}}_2$/$h$-BN/bilayer-${\mathrm{In}}_2{\mathrm{Se}}_3$/$h$-$\mathrm{BN}/{\mathrm{Fe}}_3{\mathrm{Ge}\mathrm{Te}}_2$ vdW heterostructure, and investigate the spin-dependent transport of this vdW AFMFTJ by using nonequilibrium Green’s function combined with density-functional theory. It is found that multiple resistance states are realized in this proposed vdW AFMFTJ and the considerable tunneling electroresistance ratio of about $1.0\times {10}^4\mathrm{\%}$ and the large tunneling magnetoresistance ratio of up to 695% are simultaneously achieved at zero bias. Interestingly, the regulatable negative differential conductance (NDC) by magnetic field and electric field is produced in this vdW AFMFTJ under bias voltages. The NDC effect originates from the changes in the conductive channels of ${\mathrm{Fe}}_3{\mathrm{Ge}\mathrm{Te}}_2$ electrodes and the electronic states of the ${\mathrm{In}}_2{\mathrm{Se}}_3$ barrier under different bias voltages. This work not only benefits exploring of the tunnel junction with NDC effect, but also provides a promising route for the design of multifunctional microelectronic devices based on vdW materials.

Passive metasurfaces are known for their fixed and usually single-wave manipulation functionality, which limits their potential applications for diverse scenarios. To expand the functionality of the passive metasurfaces, frequency-multiplexed technology has been proposed to encode multiple operation frequencies in a single metasurface for function selection and switching. Although this technology has been extensively utilized for electromagnetic waves, there have been few studies on designing frequency-multiplexed metasurfaces for acoustic-wave manipulation. This work applies a topology optimization method based on a multiobjective genetic algorithm (GA) to develop different frequency-encoded multifunctional acoustic metasurfaces to attain acoustic focusing and anomalous wave refraction. The effectiveness of the optimized metasurfaces is validated both numerically and experimentally. Additionally, the underlying physical mechanisms of the designed frequency-multiplexed acoustic metasurfaces are systematically analyzed. This study presents high-performance frequency-multiplexed metasurfaces for acoustic-wave-front modulation and demonstrates the promising potential of the GA-based topology optimization approach in designing integrated, miniaturized multifunctional acoustic devices for real-world applications.

Acoustic vortices (AVs) carrying orbital angular momentum (OAM) have shown great significance in communication. However, crosstalk in acoustic communication based on traditional AVs with single OAM remains an issue. Here, we propose a periodic-phase acoustic vortex (PPAV) with a comblike OAM spectrum. The sample interval of the OAM spectrum of the PPAV can be modulated by the period number of the azimuthal phase. The influence of the period number on the acoustic properties of the PPAV and the evolution of the PPAV are investigated theoretically. Moreover, an acoustic artificial-structure plate engraved with 24 filled circular holes is designed to generate the PPAV in water. By changing the height of the resin layer filling each hole unit, the transmitted phase shift of the ultrasonic wave through them can be flexibly and efficiently manipulated. Both simulations and experiments confirm that the designed artificial plate with filled holes can produce the PPAV with an arbitrary topological charge. Finally, we preliminarily explore the possibility of applying the PPAV in acoustic communication and show that the OAM sample interval of the PPAV can be used as an independent degree of freedom for acoustic encoding-decoding communication. We believe that the PPAV generated by the acoustic artificial-structure plates may find good applications in microparticle manipulation and acoustic communication.

Microwave cavities are commonly used in many experiments, including optomechanics, magnetic field sensing, magnomechanics, and circuit quantum electrodynamics. Noise, such as variations in the magnetic field or mechanical vibrations, can cause fluctuations of the natural frequency of the cavity, creating challenges in operating them in experiments. To overcome these challenges, we demonstrate a dynamic feedback system implemented by the locking of a microwave drive to the noisy cavity. A homodyne-interferometer scheme monitors the cavity resonance fluctuations due to low-frequency noise, which is mitigated by frequency modulating the microwave generator. The feedback has a bandwidth of 400 Hz, with a reduction of cavity fluctuations by $85\mathrm{\%}$ integrating up to a bandwidth of 2 kHz. Moreover, the cavity resonance frequency fluctuations are reduced by $73\mathrm{\%}$. This scheme can be scaled to enable multitone experiments locked to the same feedback signal. As a demonstration, we apply the feedback to an optomechanical experiment and implement a cavity-locked multitone mechanical measurement. As low-frequency cavity frequency noise can be a limiting factor in many experiments, the multitone microwave locking technique presented here is expected to be relevant for a wide range of microwave-cavity experiments.