SearcharxivSearch

arXiv subjects

Hua Jiang

Publications and source records attributed to Hua Jiang.

At least 19 recordsLinked to original sources

Sequential Detection-Based Iterative Blind Separation for Single-Channel Co-Frequency Signals

Existing single-channel co-frequency signal blind separation (SCSBS) algorithms struggle to balance separation accuracy, computational complexity, and robustness, while current channel state information (CSI) estimation methods lack precision. To address these limitations, we propose a sequential detection (SD)-based iterative separation (SDIS) algorithm. SDIS incorporates a delayed unscented Kalman filter (DUKF) into an iterative decision feedback framework, jointly enhancing signal separation and CSI estimation. Simulation results show that SDIS outperforms benchmarks in separation accuracy, CSI estimation accuracy, computational efficiency, and robustness. Notably, when the mean bit error rate (MBER) drops below $10^{-4}$, SDIS can tolerate at least $0.8$ dB more noise than the benchmarks.

eess.SP

Low-Complexity Sequential Detection Framework for Single-Channel Co-Frequency Signal Separation

Practical separation of single-channel co-frequency signals (SCCFSs) is hindered by the prohibitive computational complexity of benchmark algorithms. To address this issue, we propose a low-complexity separation framework based on sequential detection (SD), in which signal separation is cast as a sequential path search over a trellis. To support both hard-decision detection and log-likelihood ratio (LLR) extraction, we develop two algorithms within this framework: the SD-based separation (SDS) algorithm and its soft-output variant (SO-SDS). Furthermore, SDS employs a windowing strategy combined with dynamic pruning to concentrate computational resources on high-probability paths, thereby enabling efficient detection of transmitted symbol sequences. Building upon SDS, SO-SDS further incorporates a state completeness verification mechanism (SCVM) to estimate bit LLRs, thus facilitating subsequent soft decoding. Numerical results show that, compared to benchmark algorithms, SDS achieves significant complexity reduction without degrading separation performance, while SO-SDS offers notable computational savings with only modest LLR accuracy loss. Notably, the computational complexity advantage of the proposed algorithms over benchmark algorithms grows substantially with increasing modulation order.

eess.SP

Topological magnon noises

We develop a comprehensive formalism for magnon transport in ferromagnetic insulators driven by a temperature gradient. The formulas for magnon current and corresponding magnon noise are derived herein based on the spin Hamiltonian of a topological magnon insulator, which enables us to calculate the magnon Hall angle, to provide an explicit expression for the Fano factor, and to reaffirm the quantitative relations between magnon conductance and magnon noise. We find that the magnon current is not conserved in the presence of the Gilbert damping. Consequently, the reciprocal relation between the local and nonlocal noises, the Johnson-Nyquist formula between the conductance and the thermal noise, and the relation between the transmission coefficient and the shot noise are profoundly altered.

cond-mat.mes-hall

Superconducting triode effect in a quantum-dot Josephson junction with a biased top gate

Non-reciprocal supercurrents enable non-dissipative rectification, holding great promise for superconducting electronics. Conventionally, this non-reciprocity, termed the superconducting diode effect, requires the simultaneous breaking of time-reversal and parity symmetries. Here, we propose a superconducting triode effect in an asymmetric quantum-dot Josephson junction coupled to an additional metallic top gate, which breaks the parity symmetry while explicitly preserving time-reversal symmetry. We demonstrate that the supercurrent across this junction exhibits a strong non-reciprocal effect that can be continuously manipulated via the top gate to achieve an ideal unidirectional supercurrent, thus manifesting a superconducting triode effect. Furthermore, under radio-frequency radiation, this junction exhibits highly asymmetric Shapiro steps, realizing fully quantized supercurrent rectification. Our work not only provides an alternative physical mechanism for the superconducting diode effect observed in Josephson junctions with explicit time-reversal symmetry, but also introduces a new tuning knob to manipulate supercurrent non-reciprocity.

cond-mat.mes-hall

Zero-Field Thermal Hall Effect in Insulator

Fourier's law dictates that heat flow is usually parallel to the applied temperature gradient. However, under a high magnetic field, heat flow carried by both electrons in conductors and phonons in insulators can be deflected, a phenomenon known as thermal Hall effect. Intriguingly, we observe at zero field a spontaneous thermal Hall effect in an antiferromagnetic insulator. Despite a vanishingly small uncompensated magnetization, the magnitude of this effect is surprisingly large, comparable to typical responses induced by several teslas of external field. This zero-field behavior indicates that charge-neutral heat carriers can be governed by an intrinsic effective field arising from the unique spin arrangement. Our discovery challenges the centuries-old preconception of heat conduction and open up new avenues for exploring non-trivial topological responses in quantum materials.

cond-mat.str-el

Electron Dynamics Reconstruction and Nontrivial Transport by Acoustic Waves

Surface acoustic waves (SAWs) become a popular driving source in modern condensed matter physics, but most existing theories simplify them as electric fields and ignore the non-uniform Brillouin zone folding effect. We develop a semiclassical framework and reconstruct the electron dynamics by treating SAW as a quasi-periodic potential modulating electronic momentum distribution. This framework naturally explains the experimentally observed DC drag current and predicts acousto-electric Hall effect. The theory further reveals various SAW-driven transport phenomena, emerging anomalous Hall, thermal Hall, and Nernst effects within time-reversal symmetric systems. Illustrated in bilayer graphene and $\mathrm{MX_2}$ (M = Mo, W; X = S, Se, Te), the angular-dependent acousto-electric Hall effect provides an experimental probe for Berry curvature distribution.

cond-mat.mes-hall

GCTAM: Global and Contextual Truncated Affinity Combined Maximization Model For Unsupervised Graph Anomaly Detection

Anomalies often occur in real-world information networks/graphs, such as malevolent users, malicious comments, banned users, and fake news in social graphs. The latest graph anomaly detection methods use a novel mechanism called truncated affinity maximization (TAM) to detect anomaly nodes without using any label information and achieve impressive results. TAM maximizes the affinities among the normal nodes while truncating the affinities of the anomalous nodes to identify the anomalies. However, existing TAM-based methods truncate suspicious nodes according to a rigid threshold that ignores the specificity and high-order affinities of different nodes. This inevitably causes inefficient truncations from both normal and anomalous nodes, limiting the effectiveness of anomaly detection. To this end, this paper proposes a novel truncation model combining contextual and global affinity to truncate the anomalous nodes. The core idea of the work is to use contextual truncation to decrease the affinity of anomalous nodes, while global truncation increases the affinity of normal nodes. Extensive experiments on massive real-world datasets show that our method surpasses peer methods in most graph anomaly detection tasks. In highlights, compared with previous state-of-the-art methods, the proposed method has +15\% $\sim$ +20\% improvements in two famous real-world datasets, Amazon and YelpChi. Notably, our method works well in large datasets, Amazin-all and YelpChi-all, and achieves the best results, while most previous models cannot complete the tasks.

cs.SI

AEG: A Baremetal Framework for AI Acceleration via Direct Hardware Access in Heterogeneous Accelerators

This paper introduces a unified, hardware-independent baremetal runtime architecture designed to enable high-performance machine learning (ML) inference on heterogeneous accelerators, such as AI Engine (AIE) arrays, without the overhead of an underlying real-time or general-purpose operating system. Existing edge-deployment frameworks, such as TinyML, often rely on real-time operating systems (RTOS), which introduce unnecessary complexity and performance bottlenecks. To address this, our solution fundamentally decouples the runtime from hardware specifics by flattening complex control logic into linear, executable Runtime Control Blocks (RCBs). This "Control as Data" paradigm allows high-level models, including Adaptive Data Flow (ADF) graphs, to be executed by a generic engine through a minimal Runtime Hardware Abstraction Layer (RHAL). We further integrate Runtime Platform Management (RTPM) to handle system-level orchestration (including a lightweight network stack) and a Runtime In-Memory File System (RIMFS) to manage data in OS-free environments. We demonstrate the framework's efficacy with a ResNet-18 image classification implementation. Experimental results show 9.2$\times$ higher compute efficiency (throughput per AIE tile) compared to Linux-based Vitis AI deployment, 3--7$\times$ reduction in data movement overhead, and near-zero latency variance (CV~$=0.03\%$). The system achieves 68.78\% Top-1 accuracy on ImageNet using only 28 AIE tiles compared to Vitis AI's 304 tiles, validating both the efficiency and correctness of this unified bare-metal architecture.

cs.DC

Fundamental Relations as the Leading Order in Nonlinear Thermoelectric Responses with Time-Reversal Symmetry

In recent years, nonlinear transport phenomena have garnered significant interest in both theoretical explorations and experiments. In this work, we utilize the semi-classical wave packet theory to calculate disorder-induced second-order transport coefficients: second-order electrical ($\sigma$), thermoelectric ($\alpha$), and thermal ($\kappa$) coefficients, capturing the interplay between side-jump and skew-scattering contributions in systems with time-reversal symmetry. Using a topological insulator model, we quantitatively characterize the Fermi-level dependence of these second-order transport coefficients by explicitly including Coulomb impurity potentials. Furthermore, we elucidate the relationships between these coefficients, establishing the second-order Mott relation and the Wiedemann-Franz law induced by disorder. This study develops a comprehensive theoretical framework elucidating the nonlinear thermoelectric transport mechanisms in quantum material systems.

cond-mat.mes-hall

Label-Efficient 3D Forest Mapping: Self-Supervised and Transfer Learning for Instance Segmentation, Semantic Segmentation, and Species Classification

Detailed structural and species information on individual tree level is increasingly important to support precision forestry, biodiversity conservation, and provide reference data for biomass and carbon mapping. Point clouds from airborne and ground-based laser scanning are currently the most suitable data source to rapidly derive such information at scale. Recent advancements in deep learning improved segmenting and classifying individual trees and identifying semantic tree components. However, deep learning models typically require large amounts of annotated training data which limits further improvement. Producing dense, high-quality annotations for 3D point clouds, especially in complex forests, is labor-intensive and challenging to scale. We explore strategies to reduce dependence on large annotated datasets using self-supervised and transfer learning. Our objective is to improve performance across three tasks: instance segmentation, semantic segmentation, and tree classification using realistic and operational training sets. We observe improvements across all tasks, compared to training from scratch, evaluated with their respective metrics. For instance segmentation, self-supervised learning combined with domain adaptation improves AP50 by 16.98%. For semantic segmentation, self-supervised learning alone improves mIoU by 1.79%. For tree classification, hierarchical transfer learning improves mean Jaccard by 6.07%. To simplify use and encourage uptake, we integrated the tasks into a unified framework, streamlining the process from raw point clouds to tree delineation, structural analysis, and species classification. Pretrained models reduce energy consumption and carbon emissions by ~21%. This open-source contribution aims to accelerate operational extraction of individual tree information from laser scanning point clouds to support forestry, biodiversity, and carbon mapping.

cs.CV

Nonlinear transport fingerprints of tunable Fermi-arc connectivity in magnetic Weyl semimetal Co$_3$Sn$_2$S$_2$

Fermi arcs in Weyl semimetals provide a unique platform for surface-state engineering, yet di rectly tracking of their evolution under surface tuning remains experimentally challenging. Here we theoretically propose that nonreciprocal charge transport can serve as a direct probe of Fermi arc Lifshitz transitions (FALT). We show that different surface terminations in Co3Sn2S2 can produce f inite and highly tunable second-order nonreciprocal signals, which can be further modulated by adjusting the surface potential. Strikingly, we show that the second-order conductivity exhibits sign changes as the Fermi arc connectivity is tuned across FALT driven by gating or chemical potential variation. This behavior arises from the chiral nature of electron velocities on the Fermi arcs, and is highly sensitive to surface termination and symmetry breaking. Our findings establish nonreciprocal transport as an electrically measurable fingerprint of FALT and propose new strategies that could be directly applied in devices for in situ engineering and detecting transport properties in topological materials.

cond-mat.mes-hall

Early-stopping for Transformer model training

This work, based on Random Matrix Theory (RMT), introduces a novel early-stopping strategy for Transformer training dynamics. Utilizing the Power Law (PL) fit to tansformer attention matrices as a probe, we demarcate training into three stages: structural exploration, heavy-tailed structure stabilization, and convergence saturation. Empirically, we observe that the spectral density of the shallow self-attention matrix $V$ consistently evolves into a heavy-tailed distribution. Crucially, we propose two consistent and validation-set-free criteria: a quantitative metric for heavy-tailed dynamics and a novel spectral signature indicative of convergence. The strong alignment between these criteria highlights the utility of RMT for monitoring and diagnosing the progression of Transformer model training.

cs.LG

The fate of disorder in twisted bilayer graphene near the magic angle

In disordered lattices, itinerant electrons typically undergo Anderson localization due to random phase interference, which suppresses their motion. By contrast, in flat-band systems where electrons are intrinsically localized owing to their vanishing group velocity, the role of disorder remains elusive. Twisted bilayer graphene (TBG) at the magic angle $\sim 1.1^\circ$ provides a representative flat-band platform to investigate this problem. Here, we perform an atomistic tight-binding quantum transport calculation on the interplay between disorder and flat-bands in TBG devices. This non-phenomenological approach provides direct evidence that moderate disorder enhances conductance, whereas stronger disorder restores localization, revealing a disorder-driven delocalization-to-localization transport behavior. The underlying physical mechanism is understood by an effective inter-moir{\'e} tunneling strength via spectral flow analysis of a disordered TBG cylinder. Moreover, by comparing magic-angle and large-angle TBG, we demonstrate qualitatively distinct disorder responses tied to the presence of flat-bands. Our quantitative results highlight the unconventional role of disorder in flat-band moir{\'e} materials and offer insights into the observation of the fractional quantum anomalous Hall effect in disordered moir{\'e} systems.

cond-mat.mes-hall

Grounded AI for Code Review: Resource-Efficient Large-Model Serving in Enterprise Pipelines

Automated code review adoption lags in compliance-heavy settings, where static analyzers produce high-volume, low-rationale outputs, and naive LLM use risks hallucination and incurring cost overhead. We present a production system for grounded, PR-native review that pairs static-analysis findings with AST-guided context extraction and a single-GPU, on-demand serving stack (quantized open-weight model, multi-tier caching) to deliver concise explanations and remediation guidance. Evaluated on safety-oriented C/C++ standards, the approach achieves sub-minute median first-feedback (offline p50 build+LLM 59.8s) while maintaining competitive violation reduction and lower violation rates versus larger proprietary models. The architecture is decoupled: teams can adopt the grounding/prompting layer or the serving layer independently. A small internal survey (n=8) provides directional signals of reduced triage effort and moderate perceived grounding, with participants reporting fewer human review iterations. We outline operational lessons and limitations, emphasizing reproducibility, auditability, and pathways to broader standards and assisted patching.

cs.SE

Domain Wall Engineering in Graphene-Based Josephson Junctions

Recent progress has enabled the controlled fabrication of domain walls (DWs) in graphene, which host topological kink states. Meanwhile, reliable techniques for constructing graphene-based Josephson junctions have been established. While the experimental prerequisites for combining DWs with Josephson junctions are now available, this direction remains largely unexplored. In this work, we theoretically investigate transport properties in graphene-based Josephson junctions mediated by topological kink states and propose three DW engineering strategies. (i) DW number engineering uncovers a continuous evolution of critical current interference pattern from Aharonov-Bohm oscillation to Fraunhofer diffraction with increasing DW number, reproducing experimental observations [Barrier et al., Nature 628, 741 (2024)] and suggesting enhanced sensitivity for magnetometry applications. (ii) DW symmetry engineering demonstrates that an asymmetric configuration of DWs under magnetic field yields an ideal Josephson diode characterized by pronounced nonreciprocal transport. (iii) DW geometry engineering reveals that intersecting DWs enable controllable supercurrent splitting with ratios among leads tunable through the intersection angle, magnetic field, and superconducting phase difference. Our findings elucidate the rich physics of DW-based Josephson junctions and establish a versatile platform for next-generation quantum devices.

cond-mat.mes-hall

Topological Layer-Spin Filter in Screw Dislocation

While the quantum spin Hall effect leverages two-dimensional topological states to manipulate spin without dissipation, layertonics extends this paradigm to three dimension by enabling control over the layer degree of freedom. Topological materials incorporating screw dislocations exhibit the capability for simultaneous manipulation of both electronic spin and layer degrees of freedom. In this work, the electronic transport properties of a multilayer Kane-Mele model with screw dislocations is studied theoretically. Numerical simulations of a screw dislocation reveal that dissipationless quantum spin Hall edge states propagate not only at the outer boundaries of the structure but also along the screw dislocation itself, working as layer-spin filter. In detail, 1) the spin-up and spin-down carriers starting from the same source layer flow to different drain layers along the topological channels, respectively. 2) The spin of carriers flowing into a given drain layer is determined by the input source layer. Moreover, we found that the transmission coefficient and spin polarization remain robust against Anderson disorder. Under magnetic disorder, spin flip and backscattering occur, suppressing the transmission coefficient while maintaining nearly unchanged spin polarization. Finally, the layer- and spin-resolved transport properties in a device with two screw dislocations are investigated as well. We have developed an innovative methodology to modulate electron transport with simultaneous layer and spin resolution.

cond-mat.mes-hall

Quantized Topological States and Parity Anomaly in Intrinsic Quantum Anomalous Hall Insulator MnBi2Te4

When thinned down to just a few atomic layers, the layered magnetic topological insulator MnBi2Te4 offers an exceptional platform for exploring a wide range of topological phenomena. In this work, we overcome longstanding challenges in synthesizing high-purity MnBi2Te4 crystals and report the observation of a myriad of quantized topological states in high-quality five-septuple-layer (5-SL) samples under magnetic fields up to 45 Tesla. We show that the nontrivial topology of 5-SL MnBi2Te4, in the presence of Landau quantization, is governed by a generalized topological index rooted in the parity anomaly of Dirac fermions in (2+1) dimensions. The anomaly manifests as an anomalous Landau level, giving rise to gate-tunable helical edge transport. Our results establish high-quality MnBi2Te4 as a robust platform for exploring emergent topological states and for advancing novel quantum device applications.

cond-mat.mes-hall

Transdimensional anomalous Hall effect in rhombohedral thin graphite

Anomalous Hall effect (AHE), occurring in materials with broken time-reversal symmetry, epitomizes the intricate interplay between magnetic order and orbital motions of electrons[1-4]. In two dimensional (2D) systems, AHE is always coupled with out-of-plane orbital magnetization associated in-plane chiral orbital motions. In three dimensional (3D) systems, carriers can tunnel or scatter along the third dimension within the vertical mean free path lz. When sample thickness far exceeds lz, scattering disrupts coherent out-of-plane motion, making 3D AHE effectively a thickness-averaged 2D counterpart[4] -- still governed by out-of-plane orbital magnetization arising from in-plane orbital motions. Here, we explore an uncharted regime where the sample thickness is much larger than the atomic layer thickness yet smaller than or comparable to lz. In such "transdimensional" regime, carriers can sustain coherent orbital motions both within and out of the 2D plane, leading to a fundamentally new type of AHE that couples both out-of-plane and in-plane orbital magnetizations. We report the first observation of such phenomenon -- transdimensional AHE (TDAHE) -- in electrostatically gated rhombohedral ennealayer graphene. This state emerges from a peculiar metallic phase that spontaneously breaks time-reversal, mirror and rotational symmetries driven by electron-electron interactions. Such TDAHE manifests as concurrent out-of-plane and in-plane Hall resistance hysteresis, controlled by external magnetic fields along either direction. Our findings unveils a new class of AHE, opening an unexplored paradigm for correlated and topological physics in transdimensional systems.

cond-mat.mes-hall