arXiv subjects

Xiao Renshaw Wang

Publications and source records attributed to Xiao Renshaw Wang.

13 recordsLinked to original sources

arXiv2026

Thermal Hall Resistivity as a Unifying Description of Phonon Thermal Hall Effect in Various Insulators

A considerable phonon thermal Hall effect was recently discovered across a diverse collection of materials. To clarify this enigmatic thermal Hall response in various insulators, we investigate the doped Mott insulator La$_{5/3}$Sr$_{1/3}$NiO$_4$ as an example material system and reveal a characteristic phonon-dominated thermal Hall effect. As a sensitive probe of the transverse thermal response, the thermal Hall resistivity $w_{xy}$ exhibits an insulating-like temperature dependence $w_{xy}(T)$, a linear magnetic-field dependence $w_{xy}(H)$ near $H=0$, and a $T$-linear thermal Hall angle at low temperatures. The presence of similar phenomena across a series of insulators suggests that $w_{xy}$ serves as a unifying description of phonon thermal Hall effect, corroborated by an apparent correlation between the insulating-like $w_{xy}(T)$ and material's localized electronic state.

cond-mat.str-el↗

arXiv2026

Efficient and Robust p-type Transistor based on Ultra-wide-bandgap Semiconductor

The p-type transistor is an indispensable component of semiconductor technology, enabling complementary operation with n-channel transistors for computation, storage, and communication. Achieving both high robustness and high efficiency is highly desirable but challenging for p-type transistors due to limited semiconductors with reliable hole transport and their high activation energies. Here, we achieved a robust yet efficient p-type transistor by heterogeneously integrating an ultra-wide-bandgap semiconductor and a high-k dielectric layer through van der Waals integration. The p-type transistor employs a two-dimensional hole channel on hydrogenated diamond (bandgap 5.6 eV) combined with a high-k (30.5) SrTiO3 perovskite membrane. At room temperature, the transistor exhibits stable operation with a high on-current (~200 mA/mm), low subthreshold swing (70 mV/dec), high hole mobility (566 cm^2/Vs to 572 cm^2/Vs) and high on-off ratio (~10^9). Furthermore, tuning annealing temperature allows operation in either enhancement or depletion mode. The robust p-type transistor with high efficiency holds great potential for future power electronics, UV optoelectronics, and harsh-environment electronic applications.

cond-mat.mtrl-sci↗

arXiv2025

Hysteresis Measurements as a Diagnostic Tool: A Systematic Approach for Stability Benchmarking and Performance Projection of 2D-Materials-Based MOSFETs

Judging by its omnipresence in the literature, the hysteresis observed in the transfer characteristics of emerging transistors based on 2D-materials is widely accepted as an important metric related to the device quality. The hysteresis is often reported with attributes like "negligible" or "small" without giving any specifics as to how this was determined and against what reference the measured values were compared to. Quite surprisingly, there appears to be only a fragmentary understanding of the mechanisms actually contributing to hysteresis and the sensitivity of the actual measurement on various experimental parameters. We attempt to close this gap by first providing a comprehensive theoretical analysis of the dominant mechanisms contributing to hysteresis: charge trapping by defects from the channel or the gate, the drift of mobile charges, and eventually ferroelectricity. We continue by suggesting methods to experimentally distinguishing between these phenomena. Based on these discussions it becomes clear that previously reported hysteresis values have little meaning as they have been non-systematically recorded under arbitrary conditions. In order to resolve this predicament, we propose a standardized hysteresis measurement scheme to establish the hysteresis as a comparable metric for the assessment of device stability. Our standardized scheme ensures that hysteresis data can be effectively compared across different technologies and, most importantly, provide a means to extrapolate data obtained on thicker prototypes to subnanometer equivalent oxide thicknesses. This facilitates the systematic benchmarking of insulator/channel combinations in terms of stability, which thereby enables the screening of material systems for more stable and reliable 2D-material-based MOSFETs.

physics.app-ph↗

arXiv2025

How to Identify Suitable Gate Dielectrics for Transistors based on Two-Dimensional Semiconductors

The recent progress in nanosheet transistors has established two-dimensional (2D) semiconductors as viable candidates for future ultra-scaled electronic devices. Next to reducing contact resistance, identifying good gate dielectrics is a fundamental challenge, as the dielectric/channel interface dramatically impacts virtually all performance parameters. While several promising gate dielectrics have recently been reported, the evaluation of their quality and suitability is often fragmentary and focused on selected important performance metrics of the gate stack, such as the capacitive gate control, leakage currents, reliability, and ease of fabrication and integration. However, identifying a suitable gate stack is a complex problem that has not yet been approached systematically. In this perspective, we aim to formulate general criteria for good gate dielectrics.

physics.app-ph↗

arXiv2025

Superconducting Diode Effect in Gradiently Strained Nb0.5Ti0.5N Films

The superconducting diode effect (SDE), combining superconductivity with diode-like nonreciprocal current flow, recently emerges as an ideal candidate for zero-dissipation electronic circuits. Such technologically advantageous diodes are achieved by intricate material engineering to disrupt inversion symmetry, which leads to the production challenges as well as a limited pool of viable materials. Here we exploit the gradient interfacial strain to experimentally induce the SDE in Nb0.5Ti0.5N (NTN) films grown on MgO substrates. Additionally, the SDE is tunable with an in-plane magnetic field and can be further enhanced by introducing an interfacial anisotropic pinning potential. Our findings establish interfacial strain gradient as a versatile tool for creating and enhancing tunable SDE.

cond-mat.supr-con↗

arXiv2024

Electrical Control Grain Dimensionality with Multilevel Magnetic Anisotropy

In alignment with the increasing demand for larger storage capacity and longer data retention, electrical control of magnetic anisotropy has been a research focus in the realm of spintronics. Typically, magnetic anisotropy is determined by grain dimensionality, which is set during the fabrication of magnetic thin films. Despite the intrinsic correlation between magnetic anisotropy and grain dimensionality, there is a lack of experimental evidence for electrically controlling grain dimensionality, thereby impeding the efficiency of magnetic anisotropy modulation. Here, we demonstrate an electric field control of grain dimensionality and prove it as the active mechanism for tuning interfacial magnetism. The reduction in grain dimensionality is associated with a transition from ferromagnetic to superparamagnetic behavior. We achieve a non-volatile and reversible modulation of the coercivity in both the ferromagnetic and superparamagnetic regimes. Subsequent electrical and elemental analysis confirms the variation in grain dimensionality upon the application of gate voltages, revealing a transition from a multidomain to a single-domain state accompanied by a reduction in grain dimensionality. Furthermore, we exploit the influence of grain dimensionality on domain wall motion, extending its applicability to multilevel magnetic memory and synaptic devices. Our results provide a strategy for tuning interfacial magnetism through grain size engineering for advancements in high-performance spintronics.

cond-mat.mtrl-sci↗

arXiv2024

Field-free superconducting diode effect and magnetochiral anisotropy in FeTe0.7Se0.3 junctions with the inherent asymmetric barrier

Nonreciprocal electrical transport, characterized by an asymmetric relationship between current and voltage, plays a crucial role in modern electronic industries. Recent studies have extended this phenomenon to superconductors, introducing the concept of the superconducting diode effect (SDE). The SDE is characterized by unequal critical supercurrents along opposite directions. Due to the requirement on broken inversion symmetry, the SDE is commonly accompanied by electrical magnetochiral anisotropy (eMCA) in the resistive state. Achieving a magnetic field-free SDE with field tunability is pivotal for advancements in superconductor devices. Conventionally, the field-free SDE has been achieved in Josephson junctions by intentionally intercalating an asymmetric barrier layer. Alternatively, internal magnetism was employed. Both approaches pose challenges in the selection of superconductors and fabrication processes, thereby impeding the development of SDE. Here, we present a field-free SDE in FeTe0.7Se0.3 (FTS) junction with eMCA, a phenomenon absent in FTS single nanosheets. The field-free property is associated with the presence of a gradient oxide layer on the upper surface of each FTS nanosheet, while the eMCA is linked to spin-splitting arising from the absence of inversion symmetry. Both the SDE and eMCA respond to magnetic fields with distinct temperature dependencies. This work presents a versatile and straightforward strategy for advancing superconducting electronics.

cond-mat.supr-con↗

arXiv2023

Two-dimensional layered materials meet perovskite oxides: A combination for high-performance electronic devices

As the Si-based transistors scale down to atomic dimensions, the basic principle of current electronics, which heavily relies on the tunable charge degree of freedom, faces increasing challenges to meet the future requirements of speed, switching energy, heat dissipation, packing density as well as functionalities. Heterogeneous integration, where dissimilar layers of materials and functionalities are unrestrictedly stacked at an atomic scale, is appealing to next-generation electronics, such as multi-functional, neuromorphic, spintronic and ultra-low power devices, because it unlocks technologically useful interfaces of distinct functionalities. Recently, the combination of functional perovskite oxides and the two-dimensional layered materials (2DLMs) led to unexpected functionalities and enhanced device performance. In this review, we review the recent progress of the heterogeneous integration of perovskite oxides and 2DLMs from the perspectives of fabrication and interfacial properties, electronic applications, challenges as well as outlooks. In particular, we focus on three types of attractive applications, namely field-effect transistors, memory, and neuromorphic electronics. The van der Waals integration approach is extendible to other oxides and 2DLMs, leading to almost unlimited combinations of oxides and 2DLMs and contributing to future high-performance electronic and spintronic devices.

cond-mat.mtrl-sci↗

arXiv2022

Nonreciprocal transport in a bilayer of MnBi2Te4 and Pt

MnBi2Te4 (MBT) is the first intrinsic magnetic topological insulator with the interaction of spin-momentum locked surface electrons and intrinsic magnetism, and it exhibits novel magnetic and topological phenomena. Recent studies suggested that the interaction of electrons and magnetism can be affected by the Mn-doped Bi2Te3 phase at the surface due to inevitable structural defects. Here we report an observation of nonreciprocal transport, i.e. current-direction-dependent resistance, in a bilayer composed of antiferromagnetic MBT and nonmagnetic Pt. The emergence of the nonreciprocal response below the Néel temperature confirms a correlation between nonreciprocity and intrinsic magnetism in the surface state of MBT. The angular dependence of the nonreciprocal transport indicates that nonreciprocal response originates from the asymmetry scattering of electrons at the surface of MBT mediated by magnon. Our work provides an insight into nonreciprocity arising from the correlation between magnetism and Dirac surface electrons in intrinsic magnetic topological insulators.

cond-mat.mes-hall↗

arXiv2022

Recent Advances in Tunable Metasurfaces: Materials, Design and Applications

Metasurfaces, a two-dimensional (2D) form of metamaterials constituted by planar meta-atoms, exhibit exotic abilities to freely tailor electromagnetic (EM) waves. Over the past decade, tunable metasurfaces have come to the frontier in the field of nanophotonics, with tremendous effort focused on developing and integrating various active materials into metasurfaces. As a result, tunable/reconfigurable metasurfaces with multi-functionalities triggered by various external stimuli have been successfully demonstrated, openings a new avenue to dynamically manipulate and control EM waves for photonic applications in demand. In this review, we first brief the progress of tunable metasurfaces development in the last decade and highlight representative works from the perspectives of active materials development, design methodologies and application-driven exploration. Then, we elaborate on the active tuning mechanisms and relevant active materials. Next, we discuss recent achievements in theory as well as machine learning (ML) assisted design methodologies to sustain the development of this field. After that, we summarize and describe typical application areas of the tunable metasurfaces. We conclude this review by analyzing existing challenges and presenting our perspectives on future directions and opportunities in this vibrant and fast-developing field.

physics.optics↗

arXiv2021

Multistate Tuning of Third Harmonic Generation in Fano-Resonant Hybrid Dielectric Metasurfaces

Hybrid dielectric metasurfaces have emerged as a promising approach to enhancing near field confinement and thus achieving high optical nonlinearity using low loss dielectrics. Additional flexibility in design and fabrication of hybrid metasurfaces allows dynamic control of light, which is value-added for a wider range of applications. Here, we demonstrate a tunable and efficient third harmonic generation (THG) via hybrid metasurfaces with phase change material Ge2Sb2Te5 (GST) deposited on top of amorphous silicon nanostructutes. Fano resonance is excited to confine the incident light inside the hybrid metasurfaces, and an experimental quality factor ($Q$-factor) of 125 is achieved at the fundamental pump wavelength around 1210 nm. We demonstrate the switching between a turn-on state of Fano resonance in the amorphous state of GST and a turn-off state in its crystalline state and also gradual multistate tuning of THG emission at its intermediate state. We achieve a high THG conversion efficiency of $η = 2.9*10^{-6}$ %, which is more than ~32 times of that of a GST-based Fabry-Pèrot cavity under a similar pump laser power, thanks to the enhanced field confinement due to the Fano resonance. Our results show the strong potential of GST-based hybrid dielectric metasurfaces for efficient and tunable nonlinear optical devices.

physics.optics↗

arXiv2019

Phase-controllable growth of ultrathin 2D magnetic FeTe crystals

Two-dimensional (2D) magnets with intrinsic ferromagnetic/antiferromagnetic (FM/AFM) ordering are highly desirable for future spintronics devices. However, the synthesis of 2D magnetic crystals, especially the direct growth on SiO2/Si substrate, is just in its infancy. Here, we report a chemical vapor deposition (CVD)-based rational growth approach for the synthesis of ultrathin FeTe crystals with controlled structural and magnetic phases. By precisely optimizing the growth temperature (Tgrowth), FeTe nanoplates with either layered tetragonal or non-layered hexagonal phase can be controlled with high-quality. The two controllable phases lead to square and triangular morphologies with a thickness down to 3.6 and 2.8 nm, respectively. More importantly, transport measurements reveal that tetragonal FeTe is antiferromagnetic with a Neel temperature (TN) about 71.8 K, while hexagonal FeTe is ferromagnetic with a Curie temperature (TC) around 220 K. Theoretical calculations indicate that the ferromagnetic order in hexagonal FeTe is originated from a concomitant lattice distortion and the spin-lattice coupling. This study represents a major step forward in the CVD growth of 2D magnetic materials on SiO2/Si substrates and highlights on their potential applications in the future spintronic devices.

cond-mat.mtrl-sci↗

arXiv2019

A Synthetic Skyrmion Platform with Robust Tunability

Magnetic skyrmions are topologically non-trivial spin structure, and their existence in ferromagnetically coupled multilayers has been reported with disordered arrangement. In these multilayers, the heavy metal spacing layers provide an interfacial Dzyaloshinskii-Moriya interaction (DMI) for stabilizing skyrmions at the expense of interlayer exchanging coupling (IEC). To meet the functional requirement of ordered/designable arrangement, in this work, we proposed and experimentally demonstrated a scenario of skyrmion nucleation using nanostructured synthetic antiferromagnetic (SAF) multilayers. Instead of relying on DMI, the antiferromagnetic IEC in the SAF multilayers fulfills the role of nucleation and stabilization of skyrmions. The IEC induced skyrmions were identified directly imaged with MFM and confirmed by magnetometry and magnetoresistance measurements as well as micromagnetic simulation. Furthermore, the robustness of the proposed skyrmion nucleation scenario was examined against temperature (from 4.5 to 300 K), device size (from 400 to 1200 nm), and different lattice designs. Hence, our results provide a synthetic skyrmion platform meeting the functional needs in magnonic and spintronic applications.

cond-mat.str-el↗