Thermoreflectance techniques, such as time-domain thermoreflectance (TDTR), frequency-domain thermoreflectance (FDTR), and the square-pulsed source (SPS) method, are powerful tools for characterizing thermal properties in bulk and thin-film materials. However, accurately interpreting their signals remains challenging due to intricate interdependencies among experimental variables. This study introduces a systematic framework based on singular-value decomposition (SVD) to decouple these interdependent parameters and enhance the reliability of thermal property extraction. By applying SVD to the sensitivity matrix, we identify key parameter combinations and establish essential dimensionless numbers that govern thermoreflectance signals. The framework is applied to a $\mathrm{Ga}\mathrm{N}/\mathrm{Si}$ heterostructure, where the performance of TDTR, FDTR, and SPS are evaluated. Results show a high degree of consistency across all three techniques, with the improved understanding enabling precise and simultaneous extraction of up to seven key thermal properties, including thermal conductivity, heat capacity, and interfacial thermal conductance of the $\mathrm{Ga}\mathrm{N}/\mathrm{Si}$ multilayer system. This framework not only improves the precision of thermoreflectance measurements but also lays a foundation for advanced thermal metrology in both research and industrial applications.

Gate-all-around (GAA) configurations with superior electrostatics and scaling potential are recognized as an ultimate solution for the post-Moore complementary metal oxide semiconductor (CMOS) circuits. In this case, nanowires (NWs) with a natural dangling-bond-free surface are one of the most promising channel candidates for the ultrascaled GAA field-effect transistors (FETs). Herein, we propose that the ${\mathrm{Hf}\mathrm{Sn}\mathrm{S}}_3$ NWs are very attractive channel materials for sub-5-nm GAA FETs, exhibiting excellent n- and p-type symmetric behaviors. In particular, holding ultrahigh phonon-limited carrier mobilities, the sub-5-nm ${\mathrm{Hf}\mathrm{Sn}\mathrm{S}}_3$ NW n- and p-FETs far surpass the International Technology Roadmap for Semiconductors high-performance requirements. The on-current can exceed 1000 µA $\text{μ}{\mathrm{m}}^{-1}$ even for 3-nm nodes while maintaining an excellent n- and p-type performance ratio close to 1. Furthermore, we reveal that the superior subthreshold swing control capability of the ${\mathrm{Hf}\mathrm{Sn}\mathrm{S}}_3$ NW p-FETs is attributed to the $p_x$-orbital-induced heavy-hole effective mass. This advantage can be attractive, especially for the further scaling of CMOS technology. Meanwhile, the power and delay of the ${\mathrm{Hf}\mathrm{Sn}\mathrm{S}}_3$ NW FETs are assessed to ensure their fast-switching and energy-efficient behaviors. Our results suggest that ${\mathrm{Hf}\mathrm{Sn}\mathrm{S}}_3$ NW FETs with superior and symmetric transport performance possess promising prospects for future sub-5-nm GAA complementary transistors.

Atom-interferometer-based gyroscopes are expected to have a wide range of applications due to their high sensitivity; however, their dynamic range is limited by dephasing from the velocity-dependent Sagnac phase shift and the longitudinal velocity distribution of the atoms, restricting measurements of large angular velocities. In this study, we present a method for restoring the contrast deterioration in angular velocity measurements with interferometer gyroscopes using atomic beams. We show that by introducing a pseudorotation effect with appropriate two-photon detunings for Raman light in the interferometer, it is possible to effectively cancel the Sagnac phase shift for all atoms in the velocity distribution of the beam. Consequently, the contrast is unaffected by the rotation. Furthermore, we apply this method to an interferometer gyroscope with counterpropagating atomic beams sharing the same Raman light. It is found that the angular velocity of the system can be estimated through the detuning point where the phase difference between the two interferometers is zero. This approach ensures that the scale factor of the atom interferometer gyroscope is independent of the change in the longitudinal velocity distribution of the atomic beam. We demonstrate our technique using an interferometer gyroscope with thermal atomic beams of rubidium-87, achieving a measurement of angular velocity of $1.0{}^{\circ }/\mathrm{s}$ even with an acceleration of $0.68\mathrm{m}/{\mathrm{s}}^2$ on a three-axis rotation table. This simple and robust dispersion-compensation method with Raman-light detuning will benefit dynamic angular velocity measurements in field applications such as the inertial navigation of vehicles.

Magnetic tunnel junctions (MTJs) are key enablers of spintronic technologies used in a variety of applications, including information storage, microwave generation and detection, and unconventional computing. Here, we present experimental and theoretical studies of the quantized spin wave eigenmodes in perpendicular MTJs focusing on the coupled magnetization dynamics in the free (FL) and reference (RL) layers of the MTJ, where the RL is a synthetic antiferromagnet (SAF). Spin-torque ferromagnetic resonance (ST-FMR) measurements reveal the excitation of two spin-wave eigenmodes in response to an applied microwave current. These modes show opposite frequency shifts as a function of an out-of-plane magnetic field. Our micromagnetic simulations accurately reproduce the dependence of the mode frequencies on the magnetic field and reveal the spatial profiles of the excitations in the FL and RL. The FL and RL modes generate rectified voltage signals of opposite polarity, which makes this device a promising candidate for a tunable dual-frequency microwave signal detector. The simulations show that a weak interlayer exchange coupling within the SAF enhances the mode amplitudes. We also calculate the response of the detector as a function of an in-plane magnetic field bias and find that its sensitivity significantly grows with increasing field strength. We experimentally confirm this prediction via ST-FMR measurements as a function of the in-plane magnetic field. Our results provide a deeper understanding of the quantized spin-wave eigenmodes in nanoscale MTJs with perpendicular magnetic anisotropy and demonstrate the potential of these devices for frequency-selective dual-channel microwave signal detectors.

Developing high-performance thermoelectric (TE) materials composed of low-toxic elements alternative to $\mathrm{Pb}$-based compounds is essential for the widespread application of TE technology. Recently, a new stuffed-diamond structure ${\mathrm{Li}\mathrm{Cu}}_3{\mathrm{Ti}\mathrm{Q}}_4$ ($\mathrm{Q}$ = $\mathrm{S},\mathrm{Se}$) with moderate band gap and low hole carrier effective masses has been synthesized [J. Am. Chem. Soc. 144, 12789 (2022)], which could be a promising candidate for TE applications. Here, based on first-principle calculations combined with Boltzmann transport theory, we systematically study the electronic and thermal transport properties of ${\mathrm{Li}\mathrm{Cu}}_3{\mathrm{Ti}\mathrm{Q}}_4$ to elucidate the thermoelectric performance. The results show that the lattice thermal conductivities of ${\mathrm{Li}\mathrm{Cu}}_3{\mathrm{Ti}\mathrm{S}}_4$ and ${\mathrm{Li}\mathrm{Cu}}_3{\mathrm{Ti}\mathrm{Se}}_4$ are 2.4 and 2.1 W/mK at 300 K within the framework of the four-phonon scattering, respectively, which is comparable to various typical TE materials such as $\mathrm{Pb}\mathrm{Te}$ and ${\mathrm{Sb}}_2{\mathrm{Te}}_3$. In addition, ${\mathrm{Li}\mathrm{Cu}}_3{\mathrm{Ti}\mathrm{Q}}_4$ behaves as a degenerate semiconductor and possesses a large power factor [0.6–1.5 mW/(cm ${\mathrm{K}}^2$)] in the temperature range of 300–700 K. Consequently, the calculated figure of merit (ZT) value of p-type ${\mathrm{Li}\mathrm{Cu}}_3{\mathrm{Ti}\mathrm{Q}}_4$ can reach 0.8 at 700 K, and the ZT value could be further improved to ∼1.6 under a small strain of 3%, mostly owing to the strain-induced thermal conductivity reduction. It is also found that the lattice thermal conductivity of ${\mathrm{Li}\mathrm{Cu}}_3{\mathrm{Ti}\mathrm{S}}_4$ is abnormally lower than that of ${\mathrm{Li}\mathrm{Cu}}_3{\mathrm{Ti}\mathrm{Se}}_4$ under strain conditions, in contradiction with the conventional Keyes theory in which heavier compounds tend to have lower thermal conductivity. A comparative analysis of phonon anharmonicity of ${\mathrm{Li}\mathrm{Cu}}_3{\mathrm{Ti}\mathrm{S}}_4$ and ${\mathrm{Li}\mathrm{Cu}}_3{\mathrm{Ti}\mathrm{Se}}_4$ reveals that weakening bond stiffness, high charge transfer between the $\mathrm{Cu}$ and $\mathrm{Q}$ atoms, and a narrowing of the phonon gap lead to strong acoustic phonon scattering rates, which arises from the unique metavalent bonding in ${\mathrm{Li}\mathrm{Cu}}_3{\mathrm{Ti}\mathrm{S}}_4$. Our findings provide valuable insights into the strain-modulated anharmonic phonon dynamics and suggest promise for ${\mathrm{Li}\mathrm{Cu}}_3{\mathrm{Ti}\mathrm{Q}}_4$ as an intermediate-temperature thermoelectricity.

Understanding heat transfers in fibrous materials, particularly conduction, is a major challenge due to their heterogeneous and multiscale nature, and the unknown contribution of fiber-to-fiber contacts. In most previous modeling studies, the existence of thermal contact resistance is not considered, and the computational complexity limits the size of simulated samples, which often leads to imprecise or inaccurate predictions. The same problem arises when considering electrical conduction through fibrous materials. In this work, we describe a computationally efficient simulation approach based on a multinodal representation to analyze the steady-state heat conduction through the solid structure in numerically generated three-dimensional fibrous networks, including contact resistance. We show that the solid conductivity in these networks is governed by a master curve that depends on a single parameter: a characteristic ratio representing the interplay between the intrinsic fiber conductivity and contact resistance as well as the influence of other geometric parameters, which numerically validates previous theoretical studies. However, we observe a deviation to this established theory for poorly connected networks. We derive an expression for a correction factor, considering the influence of correlations between fiber temperatures, and we then find good agreement with our simulation data. Our results demonstrate that the solid conductivity can be fully predicted based on geometric quantities, regardless of the extent of network connectivity, thus generalizing previous studies on this topic. This work, contributing to improve our understanding of conductive heat transport in fibrous media, may prove useful in the development of accurate predictive models and optimization strategies for fibrous insulation materials.

Quantum sources with strong correlations are essential but delicate resources in quantum information science and engineering. Decoherence and loss are the primary factors that degrade nonclassical quantum correlations, with scattering playing a role in both processes. In this work, we present a method that leverages long short-term memory, a machine-learning technique known for its effectiveness in time-series prediction, to mitigate the detrimental impact of scattering in quantum systems. Our setup involves generating two-mode squeezed light via four-wave mixing in warm rubidium vapor, with one mode subjected to a scatterer to disrupt quantum correlations. Mutual information and intensity-difference squeezing between the two modes are used as metrics for quantum correlations. We demonstrate a 74.7% recovery of mutual information and an 87.7% recovery of two-mode squeezing, despite significant photon loss that would otherwise eliminate quantum correlations. This approach marks a significant step toward recovering quantum correlations from random disruptions without the need for hardware modifications, paving the way for practical applications of quantum protocols.

Heterojunctions of two-dimensional (2D) materials have generated substantial research interest due to their diverse and novel properties. In this study, we propose a class of superconductor-semiconductor-superconductor (SSS) lateral heterojunction diodes based on $M{\mathrm{Si}}_2{\mathrm{N}}_4$ ($M$ = $\mathrm{Ta},\mathrm{Mo}$, $\mathrm{W}$) monolayers. Using the ab initio method, we simulate the time- and angle-resolved photoelectron spectroscopy (Tr-ARPES) for all $M{\mathrm{Si}}_2{\mathrm{N}}_4$ monolayers and, importantly, reveal the one-band and two-gap s-wave superconductivities in ${\mathrm{Ta}\mathrm{Si}}_2{\mathrm{N}}_4$. Furthermore, these SSS diodes exhibit a significant and tunable negative differential resistance (NDR) effect. Our findings suggest that $M{\mathrm{Si}}_2{\mathrm{N}}_4$ monolayers are promising platforms for studying superconducting materials and NDR-based nanodevices, further broadening the potential applications of the ${\mathrm{MA}}_2{\mathrm{Z}}_4$ family of materials in nanoelectronics.

Stroboscopic pump-probe measurements are a well-established means of studying magnetic phenomena on subpicosecond timescales but are typically reliant on a constant external magnetic field to reset the magnetic state after application of each pump pulse. Here, a microcoil is presented that can generate a pulsed reset field with a duration of $2.1\text{μ}\mathrm{s}$ and an amplitude greater than 160 mT, at kilohertz repetition rates. Operation of the device is demonstrated through magnetic switching measurements recorded with a continuous-wave laser and a detector connected to an oscilloscope. Studies of ferromagnetic multilayer thin films and a ferrimagnetic insulating garnet film, each with perpendicular magnetic anisotropy, reveal distinctly different switching behavior that is understood in terms of the different domain configurations and dynamics within the materials. Such measurements are essential to ensure effective reset before pump-probe measurements may be attempted and inform the choice of samples for studies of ultrafast magnetic switching.

We report on a laser-frequency-stabilization and phase-noise-filtering scheme at 871 nm for high-quality quantum operations with an optical ${}^2{\mathrm{S}}_{1/2}$–${}^2{\mathrm{D}}_{3/2}$ qubit in the ${}^{171}\mathrm{Yb}{}^{+}$ ion. The phase noise of the laser field in a frequency range close to the trapped ion’s secular frequencies (0.5–2 MHz) causes undesirable excitations and thus reduces the fidelities of both single- and two-qubit gates. The most common way to overcome this problem is to filter this noise by passing the laser light through a cavity that suppresses high-frequency phase noise and provides a pure laser spectrum. Usually, the same cavity also serves as a reference for long-term frequency stabilization. We propose and characterize an improved laser-stabilization scheme consisting of (i) a reference laser locked to a high-finesse optical cavity providing a narrow linewidth and long-term frequency stability and (ii) a main laser locked to a tunable medium-finesse cavity for phase-noise filtering. The phase locking of the medium-finesse cavity resonance to the reference laser transfers its long-term stability to the main laser. This approach allows independent optimization of both the phase-noise filtering and long-term frequency-stabilization processes, as well as ensuring the robustness of the setup. The resulting laser spectrum is characterized by direct spectroscopy of an ${}^{171}\mathrm{Yb}{}^{+}$ ion in a linear Paul trap. We estimate the expected two-qubit gate infidelity with the filtered laser field to be well below 1%.

Detection of single-electron charges in solid-state nanodevices is a key technique in semiconductor quantum bit readout for quantum information processing and probing electronic properties of nanostructures. This detection has been achieved using gate-based readouts and sensitive charge sensors including quantum dot charge sensors, with their detection speed enhanced by high-speed rf reflectometry. Recently, real-time processing of data from rf reflectometry has attracted much attention to quantum information processing. In this paper, we propose a sequential method based on Bayes’ theorem for estimating the charge state and compare its performance with the averaging approach and threshold judgment. When the noise variance differs between the empty and occupied states, the Bayesian approach demonstrates a lower error score, facilitating the extraction of more data points in real-time charge state estimation. In addition, the Bayesian approach outperforms the averaging method and threshold judgment in terms of error rates for charge state estimation, even during charge transitions. This technique is broadly applicable to single-electron detection and holds substantial utility for quantum bit readout and the operation of nanoprobes that utilize single-electron detection.

We theoretically explore the photothermoelectric effect (PTE) of topological semimetals using the static two-temperature model. The interaction between the Dirac or Weyl fermions and electromagnetic waves is described by the dielectric constant in the model Hamilton of topological semimetals. Numerical calculations predict a significant PTE in the conventional plasmon mode with infrared bands of both the Dirac and Weyl semimetals. In addition to the PTE with a plasmon mode, the Weyl semimetals exhibit an enormous PTE at the frequencies of the two unconventional modes (helicon waves) in the infrared region. The helicon-wave modes originate from the resonant coupling between left- and right-circularly polarized electromagnetic waves and the helical motion of Weyl electron under an effective magnetic field induced by the Berry curvature. The frequencies of the helicon-wave modes depend on the carrier concentration, the Fermi velocity, and the distance between the positive and negative Weyl points in the Weyl semimetals, as well as the transport lifetime of the Weyl fermion. Using real parameters for the topological semimetals, we propose ideal materials for detecting the specific infrared bands of electromagnetic waves. This work strongly suggests that topological semimetals are promising for detecting electromagnetic waves in the infrared region, taking advantage of their significant PTE.

Generation and control of entanglement are fundamental tasks in quantum information. In this paper, we propose a novel approach to generating controllable frequency-entangled photons using the concept of synthetic frequency dimension in an optical system. This system consists of a ring resonator made of tailored third-order nonlinear media to induce photon-photon interactions and a periodic modulator to manipulate coupling between different frequency modes. We show that this system provides a unique platform for the exploration of distinct few- or many-body quantum phases including chaos, localization, and integrability in a highly integrable photonics platform. In particular, we develop a proposal to calculate the spectral form factor, which characterizes the degree of chaos in the system and differentiates between these phases based on observable measurements. Then, the switching of the quench dynamics from an intermediate phase between integrable and chaotic to the Stark many-body phase can generate and sustain stable frequency-entangled multiphoton states. This work is the first to explore rich and controllable quantum phases beyond single-particle physics in a synthetic dimension.

We realize single-crystal freestanding $\mathrm{Ni}\mathrm{O}$ films on $\mathrm{Si}\mathrm{N}$ membranes, enabling thin-film scattering experiments with little or no substrate background signal. These membrane samples provide a critical platform for performing ultrafast electron diffraction (UED) to probe the response of the lattice to laser excitation. We show that epitaxial $\mathrm{Ni}\mathrm{O}$ films on a water-soluble ${\mathrm{Sr}}_2{\mathrm{Ca}\mathrm{Al}}_2{\mathrm{O}}_6$ buffer layer on ${\mathrm{Sr}\mathrm{Ti}\mathrm{O}}_3$ substrates can be transferred as freestanding films to the $\mathrm{Si}\mathrm{N}$ membranes while maintaining the epitaxial character of the films. An above-gap photoexcitation ($\lambda =266\mathrm{nm}$) incident on the sample stimulates an initial lattice response of the order of 1.1 ps, followed by the persistence of this state for more than 20 ps. We observe typical Debye-Waller behavior in peaks with $q$ above the (220) family, but a distinct deviation from this behavior is seen in low-$q$ peaks. We relate this behavior to a dynamic decrease in sample mosaicity in response to the optical pump of the order of 3% that endures for approximately $4\mathrm{ps}$. We suspect that this dynamic mosaicity is due to laser-induced strain propagation. This work demonstrates the viability of the thin-film transfer method for UED and paves the way for the study of the dynamic response of antiferromagnetic thin-film oxides.

Owing to the versatile transport process, tunneling transistors (TTs) have become important building blocks for modern electronic, optoelectronic, and magnetic technologies. Although various TTs have been developed, their device operation still has challenges in terms of stability and reliability due to the tunneling process being susceptible to material size and interface scatterings. The robust edge channels in a topological insulator (TI) hold novel tunneling physics, but their TTs are still lacking. In this theoretical work, we propose topological tunneling and resonant TTs by using edge states (ESs) as transport channels in the quantum point contact (QPC) constriction. The finite size effect is the key to adjusting the band structure and tunneling barrier height of ESs by controlling the QPC width. By using the Bernevig-Hughes-Zhang (BHZ) model, we explore the single-QPC tunneling and double-QPC resonant tunneling transport, as well as their device characteristics via the quantum transport Kwant package. Topological TTs based on a single QPC possess excellent gate-modulated capability as well as a size-dependent current sensitivity of $0.1{\mathrm{nm}}^{-1}$, several orders of magnitude lower than the conventional TTs. The transport results show that the tunneling probability is significantly influenced by the QPC width (barrier height) but is weakly dependent on the QPC length (barrier width). Moreover, topological resonant TTs are designed in a double-QPC structure and show a negative differential resistance with a large peak-valley current ratio $(>{10}^4)$. The transmission spectrum exhibits multiple peaks due to the resonant tunneling driven by quantum well states. The distance between two QPCs can shift these resonant peaks by modulating the transverse confined effect. This study opens a window for designing stable, reliable, and high-performance tunneling devices via emerging quantum materials with great potential for low-power topological electronics applications.

Quantum signal processing (QSP), which enables systematic polynomial transformations on quantum data through sequences of qubit rotations, has emerged as a fundamental building block for quantum algorithms and data reuploading quantum neural networks. While recent experiments have demonstrated the feasibility of shallow QSP circuits, the inherent limitations in scaling QSP to achieve complex transformations on quantum hardware remain an open and critical question. Here we report the first experimental realization of deep QSP circuits in a trapped-ion quantum simulator. By manipulating the qubit encoded in a trapped ${}^{43}{\mathrm{Ca}}^{+}$ ion, we demonstrate high-precision simulation of some prominent functions used in quantum algorithms and machine learning, with circuit depths ranging from 15 to 360 layers and implementation times significantly longer than the coherence time of the qubit. Our results reveal a crucial trade-off between the precision of function simulation and the concomitant accumulation of hardware noise, highlighting the importance of striking a balance between circuit depth and accuracy in practical QSP implementation. This work addresses a key gap in understanding the scalability and limitations of QSP-based algorithms on quantum hardware, providing valuable insights for developing quantum algorithms as well as practically realizing quantum singular value transformation and data reuploading quantum machine learning models.

The absorption of elastic waves is fundamental to vibration attenuation in solid structures. An elastic metasurface with a more compact size has been proposed for the design of a high-efficiency absorber on the edge of a plate. However, efficient absorption of the elastic waves inside a certain region of a plate remains a challenge, as follows from the maximum absorption capped at 0.5 for the transmission problem. To realize highly efficient absorption of the transmitted elastic waves, we here propose a lossy hybrid elastic metasurface consisting of a connecting-beam cell (to perform the transmission problem) and a cantilever-zigzag cell (to mimic the reflection problem) in each supercell. The connecting-beam cell is designed to maintain a low transmission coefficient, and the cantilever-zigzag cell is utilized for high-efficiency absorption of the reflected waves. By arranging the period of the supercell, high-order diffractions of the elastic waves are suppressed, making it a one-way omnidirectional absorber. The absorption coefficients could exceed 0.5 for incidence angles between −80° and 80° within the frequency range of 3.1–5.9 kHz. In addition, an optimized symmetric supercell is designed to realize omnidirectional absorption of the elastic waves, with absorption coefficients up to 0.98. A series of experiments are also carried out to verify the high-efficiency absorption characteristics of the proposed lossy hybrid metasurface, which are in agreement with the simulation results. Our work provides a novel strategy for the efficient absorption of the transmitted elastic waves, holding great potential for mechanical vibration suppression.

Optical scattering limits the formation of optical focus to approximately 1 mm within biological tissue, posing challenges for deep-tissue optical imaging, manipulation, and therapy. To address this limitation, wavefront shaping combined with suitable guide stars shows promise. Among existing guide stars, fluorescent particles are favored for their controllable size and biological compatibility. However, they are prone to photobleaching and exhibit a broadband emission spectrum. In this study, we propose using upconversion nanoparticles (UCNPs) as alternative guide stars to mitigate the drawbacks of fluorescent particles while retaining their advantages. Through numerical simulations and empirical experiments, we demonstrate that the UCNPs effectively assist wavefront shaping in focusing scattered light, achieving a spot size of 5 µm and an enhancement factor of 48. Due to their reduced photobleaching, excellent photochemical stability, and clean emission background, the UCNPs serve as valuable supplements to existing guide stars in wavefront shaping, particularly for biomedical imaging and optical manipulation.