arXiv subjects

Ruixue Li

Publications and source records attributed to Ruixue Li.

9 recordsLinked to original sources

arXiv2026

Magnetically induced Circular Photogalvanic Effect in Symmetric Two-dimensional Materials

Photocurrents that depend on the helicity of the incident light can be generated in both bulk and low-dimensional materials lacking inversion symmetry, known as the circular photogalvanic effect (CPGE). We propose that by employing a magnetic effect, the limitation on the inversion symmetry broken materials can be overcome, such that helicity-dependent photocurrent can be generated in a symmetric material, i.e., a magneto-circular photogalvanic effect (MCPGE). As a proof of principle, we elucidate the mechanism of such an MCPGE through an effective Hamiltonian of a monolayer SbH on a magnetic substrate with an adjustable magnetization. Moreover, the associated response in optical absorption is analyzed, both single-particle and excitonic, through a Bethe-Salpeter equation to describe the Coulomb interaction in excitons. Our result broadens the mechanism of CPGE and opens new opportunities for optoelectronic devices.

cond-mat.mes-hall↗

arXiv2026

Relaxed Control with Entropy Regularization for It\^o Stochastic Systems with Input Delay

This paper investigates the infinite-horizon classical stochastic optimal control problem with input delay under an entropy-regularized relaxed control framework. In particular, by constructing a relaxed system and introducing an entropy regularization term, we reformulate the classical optimal control problem into an entropy regularized formulation, and derive the optimal controller that follows a Gaussian distribution. Furthermore, we show that the optimal Gaussian control distribution converges to the optimal Dirac measure as the exploration weight tends to zero. Numerical simulation is provided to validate the effectiveness of the proposed method.

math.OC↗

arXiv2026

Distributed Algorithm for the Global Optimal Controller of Nonlinear Multi-Agent Systems

In this paper, we investigate the distributed optimal control problem for a kind of nonlinear multi-agent systems. In particular,both the state and the system dynamic structures of each agent are private and can only be shared among communicating agents.This type of information structure is inevitable in fields such as collaborative control for industrial confidentiality, and renders traditional distributed control methods using all systems' dynamic structures ineffective. The primary contribution is the proposal of a distributed algorithm for the global optimal controller under such practical information structure via distributed approximation of the Hamilton-Jacobi-Bellman equation. Practical numerical simulation demonstrates the effectiveness of the proposed algorithm.

math.OC↗

arXiv2026

Profound impacts of interlayer interactions in bilayer altermagnetic V2S2O

Two-dimensional altermagnets exhibit exceptional potential for low-power spintronics via nonrelativistic spin splitting and zero net magnetization. Here, we systematically investigate the influence of interlayer interactions on the electronic, magnetic and quantum transport properties of bilayer vanadium oxysulfide (V2S2O), a prototypical layered altermagnet, using DFT and NEGF calculations. Our results reveal that interlayer interactions predominantly modulate the p-orbital derived top valence bands, inducing a profound competitive valence band maximum position between Gamma-point pz and X/Y-point pxy orbitals, with an energy difference as small as 9 meV. Furthermore, interlayer interactions suppress the piezomagnetic effect and impose additional requirements on the type of strain for the bilayer system, compared to its monolayer counterpart. Out-of-plane external electric fields effectively weaken interlayer coupling by enlarging the energy difference of Gamma/X-Y top valence bands to 170 meV. Quantum transport simulations on a bilayer Au/V2S2O/Au two-probe device demonstrate the presence of pronounced spin current. Interlayer interactions reduce the transmission spin polarization from nearly 100% (monolayer) to 60% (bilayer) for energies above the Fermi level. Notably, gate-voltage modulation exhibits significant asymmetry in controlling charge-to-spin current conversion efficiency, originating from the out-of-plane symmetry breaking induced by the electrode geometry. Specifically, a positive gate voltage markedly enhances the contribution of the bottom layer to the overall spin polarization, while a negative gate voltage induces a marginal reduction of transmission spin polarization, attributed to the inherently weak polarization contribution of the bottom layer. These findings provide essential insights for the design and optimization of multilayer altermagnetic spintronics.

cond-mat.mtrl-sci↗

arXiv2025

WSe2 p-MOSFETs with Nb-Doped WS2 Contacts Deposited using Atomic Layer Deposition

WSe2 p-MOSFETs with Nb-doped WS2 contacts formed using atomic layer deposition are demonstrated. The devices are fabricated using a technique that aligns the contact metallization with the Nb-doped WS2 contacts using a selective oxidation process. Devices with source/drain spacing of 0.15 um have on-state current of 103 uA/um at VDS = -1 V at a channel carrier concentration of ~ 7.5 x 1012 cm-2. The results provide a promising CMOS-compatible pathway to create low-resistance contacts to 2D-channel transistors.

cond-mat.mtrl-sci↗

arXiv2024

Dielectrophoresis-Enhanced Graphene Field-Effect Transistors for Nano-Analyte Sensing

Dielectrophoretic (DEP) sensing is an extremely important sensing modality that enables the rapid capture and detection of polarizable particles of nano-scale size. This makes it a versatile tool for applications in medical diagnostics, environmental monitoring, and materials science. Because DEP relies upon the creation of sharp electrode edges, its sensitivity is fundamentally limited by the electrode thickness. Graphene, with its monolayer thickness, enables scaling of the DEP force, allowing trapping of particles at graphene edges at ultra-low voltages. However, to date, this enhanced trapping efficiency of graphene has not been translated into an effective sensing geometry. Here, we demonstrate the expansion of graphene DEP trapping capability into a graphene field effect transistor (GFET) geometry that allows the trapped particles to be electrically detected. This four-terminal multi-functional hybrid device structure operates in three distinct modes: DEP, GFET, and DEP-GFET. By segmenting the channel of the GFET into multiple parallel channels, greatly increased density of particle trapping is demonstrated using fluorescence microscopy analysis. We show further enhancement of the trapping efficiency using engineered "nano-sites," which are holes in the graphene with size on the order of 200-300 nm. Scanning electron microscope analysis of immobilized gold nanoparticles (AuNPs) shows trapping efficiency >90% for properly engineered nano-sites. Using nano-site trapping, we also demonstrate real-time, rapid electrical sensing of AuNPs, with >2% current change occurring in 4.1 seconds, as well as rapid sensing of a variety of biomolecule-coated nanoparticles. This work shows that graphene DEP is an effective platform for nanoparticle and bio-molecule sensing that overcomes diffusion-limited and Brownian motion-based interactions.

cond-mat.mes-hall↗

arXiv2024

Manipulating the Optical Response of TaIrTe4 Heterostructures through Band Alignment Strategy

Weyl semimetals, such as $TaIrTe_{4}$, characterized by their unique band structures and exotic transport phenomena, have become a central focus in modern electronics. Despite extensive research, a systematic understanding of the impact of heterogeneous integration on the electronic and optical properties of TaIrTe4 device remains elusive. We have carried out density functional theory combined with nonequilibrium Green's function formalism calculations for $TaIrTe_{4}/WTe_{2}$, $TaIrTe_{4}/MoTe_{2}$ and $TaIrTe_{4}/h-BN$ heterostructures, aiming to understand the manipulation of photoresponse through various band alignment strategies. The underlying impacts of interlayer interactions, charge transfer and build-in electric field on the electronic properties are carefully investigated. We design a dual-probe photodetector device to understand the overall photoresponse enhancement of the heterogeneous integration by decomposing into the specific strain, interlayer transition, band overlap and symmetry lowering mechanics. These van der Waals integrations provide an ideal platform for studying band alignment physics in self-powered optoelectronic devices.

cond-mat.mtrl-sci↗

arXiv2024

CollectiveSFT: Scaling Large Language Models for Chinese Medical Benchmark with Collective Instructions in Healthcare

The rapid progress in Large Language Models (LLMs) has prompted the creation of numerous benchmarks to evaluate their capabilities.This study focuses on the Comprehensive Medical Benchmark in Chinese (CMB), showcasing how dataset diversity and distribution in supervised fine-tuning (SFT) may enhance LLM performance.Remarkably, We successfully trained a smaller base model to achieve scores comparable to larger models, indicating that a diverse and well-distributed dataset can optimize performance regardless of model size.This study suggests that even smaller models may reach high performance levels with carefully curated and varied datasets. By integrating a wide range of instructional content, our approach addresses potential issues such as data quality inconsistencies. Our results imply that a broader spectrum of training data may enhance a model's ability to generalize and perform effectively across different medical scenarios, highlighting the importance of dataset quality and diversity in fine-tuning processes. We open-source the model for future research at https://github.com/CAS-SIAT-XinHai/CollectiveSFT

cs.CL↗

arXiv2014

Desynchronization in an ensemble of globally coupled chaotic bursting neuronal oscillators by dynamic delayed feedback control

In this paper, we propose a dynamic delayed feedback control approach for desynchronization of chaotic-bursting synchronous activities in an ensemble of globally coupled neuronal oscillators. We demonstrate that the difference signal between an ensemble's mean field and its time delayed state, filtered and fed back to the ensemble, can suppress the self-synchronization in the ensemble. These individual units are decoupled and stabilized at the desired desynchronized states while the stimulation signal reduces to the noise level. The effectiveness of the method is illustrated by examples of two different populations of globally coupled chaotic-bursting neurons. The proposed method has potential for mild, effective and demand-controlled therapy of neurological diseases characterized by pathological synchronization.

nlin.CD↗