Advanced Physics Research最新文献

Terahertz (THz) dual-comb spectroscopy has been revolutionized by adaptive sampling, which enhances measurement precision and relaxes the requirement for ultra-stable lasers. However, conventional adaptive clock schemes, reliant on analog electronics, are limited by bandwidth and inherent electronic/thermal noise. To overcome these limitations, we introduce a fully digital adaptive clock implemented on a field-programmable gate array platform. Following time correction in sampling, we achieved a THz dual-comb spectroscopy system spanning 1.6 THz with 24,191 resolved comb lines and a uniform spacing of 66.14 MHz. Our system demonstrates remarkable pulse-period stability (1.15 × 10⁻¹⁰ at 32 s integration time) and a comb-line resolution at the kHz level. This all-digital solution replaces complicated analog circuitry with a compact and reconfigurable digital architecture, enabling portable, high-precision THz spectrometers capable of real-time molecular fingerprints in field applications while maintaining laboratory-grade accuracy.

By expanding magnetic nanostructures into the third dimension, it is possible to introduce new interactions and realize new forms of magnetic textures and emergent phenomena. Consequently, this unlocks new opportunities for applications in data storage, unconventional computing and sensing by utilizing 3D devices with enhanced functionalities. Connected magnetic nanowires offer a unique platform for applications such as neuromorphic computing due to their tunability and the presence of multiple transport pathways. However to realize this promise, it is necessary to further our understanding of how to locally control the magnetization in 3D, nanowire-based geometries. In this work we show the formation of magnetic domain walls, vortices, anti-vortices, and linked vortex-anti-vortex pairs in interconnected helical nanowire arrays. We show how wire diameter and 3D geometric design can control the states that form and reveal the magnetization reversal mechanism. Hence, we demonstrate this to be a highly tunable system, where the magnetization can be readily reconfigured by an external magnetic field.

This study offers new insights into the ferroelectric (FE) properties of hafnia-zirconia (HZO)-based capacitors across a wide temperature range- from room temperature (RT) to cryogenic conditions (40 K)- through advanced characterization techniques. A reversal polarization method is introduced to isolate the polarization arising exclusively from ferroelectric domain switching, eliminating back-switching and dielectric contributions. We show that, in a pristine state, remanent polarization increases at low temperature due solely to a reduction in back-switching currents, while reversal polarization is enhanced at higher temperatures due to thermally-activated depinning of FE domains. Synchrotron GIWAXS measurement reveals no detectable phase transition in HZO thin film down to 93 K, despite a reduction in the dielectric constant. The observed modifications in hysteresis loop shape and transient current are attributed to a two-step switching mechanism described by Landau-Ginzburg-Devonshire (LGD) theory, which supports the stabilization of polar phases at low temperature. Finally, the suppression of the wake-up effect at cryogenic temperatures is attributed to reduced charge trapping and/or limited oxygen vacancy redistribution within the HZO layer, highlighting the potential of ferroelectric memory for low-temperature applications.

Superconductor-Based Thermal Diode

In Research Article e00080, Yoshikazu Mizuguchi and co-workers report the experimental observation of thermal rectification in a bulk-superconductor-based thermal diode. The cover illustrates the Pb-Al thermal diode where the cooler part is superconducting Pb, and the hotter part is normal-conducting Al. Because of low thermal conductivity of a superconductor, the resulting effective thermal conductivity is lower than the opposite heat flow where the cooler part is normal-conducting Al, and the hotter part is normal-conducting Pb.

This article proposes a dual-polarization broadband frequency selective rasorber (FSR) based on a composite metasurface structure, achieving ultra-wide absorption bands on both sides of the transmission band. The vertically stacked configuration consists of a lossy layer and a frequency selective surface (FSS) layer. The top lossy layer uses compact electric resonators with coupling capacitors, while the lower FSS layer features a Jerusalem cross-slot structure, both designed to enhance absorption bandwidth. To elucidate the underlying physical mechanism, an accurate equivalent circuit model (ECM) is established, combined with surface current distribution analysis to interpret the absorption behavior. Simulation results show that the proposed FSR achieves a $$ dB reflection band over 3.68–16.94 GHz with a fractional bandwidth of 128.6%, featuring a minimum insertion loss of 0.3 dB at 10.3 GHz. The design achieves the widest low-reflection bandwidth among reported two-layer FSRs without increasing structural complexity. A prototype was fabricated and measured, showing reasonable agreement with simulations. The proposed FSR exhibits potential in broadband stealth radomes and anti-interference systems.

Ultrafast optical excitation is widely used to manipulate electronic and magnetic properties of materials on femtosecond timescales. In this study, we investigate the response of copper to circularly polarized femtosecond pulses using time-resolved magneto-optical Kerr effect measurements. We compare the dynamics induced by single-pulse excitation with those resulting from a dual-pump configuration, in which two pulses arrive simultaneously from different directions. Although the individual contributions of the two pumps are similar when applied separately, their combined effect leads to a marked change in the spin/orbital dynamics. Specifically, we observe an approximately 2.5-fold increase in the decay time of the spin/orbital imbalance signal under dual-pump excitation. This result indicates that the joint action of two optical pulses can qualitatively alter the relaxation pathways in the system, beyond a simple additive response. The observed behavior highlights a previously unexplored regime of light-induced dynamics and suggests new strategies for controlling ultrafast processes in solids.

The emergence of intrinsic 2D magnetic materials has opened new avenues for spintronic applications. Among them, Cr_1+δTe₂ has attracted significant interest due to its near-room-temperature ferromagnetism and widely-tunable chemical stoichiometry. In this work, we demonstrate a comprehensive study on the controlled modification of magnetic and electronic transport properties in 2D Cr_1+δTe₂ through focused Ga⁺ ion irradiation. Specifically, we achieved a progressive reduction and eventual full suppression of the anomalous Hall effect (AHE) sign-reversal temperature via modulating the irradiation dose, while the Curie temperature remains notably stable. Cross-sectional and elemental mapping analyses revealed irradiation-induced structural and compositional changes, highlighting the potentially distinct role of structural amorphization and stoichiometric variation in mediating the AHE behavior and magnetic ordering. The discovery of residual magnetism and tunable AHE in the amorphized structures establishes focused ion beam irradiation as a viable method for designing crystalline/amorphous architectures, offering great promise for the design of novel functionalities.

This study investigates the plasmonic properties of TiN thin films deposited by pulsed mid-frequency reactive magnetron sputtering combined with RF inductively coupled plasma in a DC magnetic field and electron cyclotron wave resonance (ECWR). The substrate was grounded while the plasma potential was tuned by applying a positive DC bias from 0 to 120 V to the ECWR coil relative to ground. Raising the DC bias increased the plasma potential and thus accelerated ions to energies corresponding to that potential, producing energetic ion bombardment of the grounded substrate. The principal benefit of adding ECWR plasma and a DC bias is an increased degree of ionization in the reactive plasma. Consequently, the resulting denser plasma and enhanced N₂ dissociation improve the internal structure of the deposited films even at low substrate temperatures.

The current market launch of HfO₂ -based ferroelectric devices relies on the control of the inherent oxygen vacancies (OVs) and their impact on the ferroelectric performance. Due to the necessary stabilization of the ferroelectric phase by doping, several dopants are investigated for their applicability to control the vacancy concentration. Hf $$ signatures in X-ray photoemission spectra are often used as an indication of OVs for both qualitative and quantitative analysis. The analysis of Y doped HfO₂ (Y:HfO₂) as investigated by hard x-ray photoelectron spectroscopy (HAXPES) reveals the inapplicability of the Hf $$ signature for a quantitative determination of OVs in the case of heterovalent doping and is restricted to pure HfO₂ or isoelectronic substitution of Hf by, for example, Zr.