arXiv subjects

Zhihao Yan

Publications and source records attributed to Zhihao Yan.

9 recordsLinked to original sources

arXiv2026

Universal scaling of the Anomalous Hall voltage of magnetic layer with the adjacent conducting layer

The anomalous Hall voltage of magnetic heterostructures plays a key role as the indicator for the magnetization state and its interplay with a variety of spintronic effects. In this letter, we report the observation, mechanism, and impact of the universal, dramatic scaling of the anomalous Hall voltage of magnetic heterostructures with the thickness and resistivity of the nonmagnetic conducting layers (e.g., normal metal) by combining transport experiments, analytical derivation, and finite-element analyses. We identify that the mechanism is the serial resistor effect of the magnetic and non-magnetic layers within the magnetic heterostructures and irrelevant to any Fermi surface variation or angular momentum injection from the nonmagnetic layer to the magnetic layer. We also show that the accuracy of the harmonic Hall voltage analyses of magnetic heterostructures are unaffected by the under-measuring of the anomalous Hall voltage and other transverse voltages due to the serial resistor effect. These findings provide crucial information for understanding a variety of spintronic phenomena involving the anomalous Hall and other transverse voltages.

cond-mat.mes-hall↗

arXiv2026

Negligible current-induced torque from the bulk and interface of Al

The light metal Al was predicted to have strong orbital Hall and Rashba effects from its bulk and interface, respectively. In this letter, we report experimental evidence that neither the bulk nor the interface of the Al contributed a detectable torque on adjacent Co and FePt layers with significant spin Hall effect, spin-orbit coupling, and resistivity mismatch with Al. These results suggest minimal orbital-spin conversion in Al and negligible orbital transport and spin-vorticity torque in Co/Al, Al/Co, and Al/FePt bilayers. Our findings suggest poor generality and/or effectiveness of torque contributions by the orbital Hall effect, the interfacial orbital Rashba effect, and the spin-vorticity coupling.

cond-mat.mes-hall↗

arXiv2026

Absence of orbital current torque in a magnetic metal/Pt/CuOx trilayer

Naturally oxidized copper (CuOx) was cited as an exceptionally strong orbital-current source despite the keen debate over the concept of orbital current. Here, we report unambiguous experimental evidence for the absence of a detectable orbital-current torque in the Fe/Pt/CuOx trilayers. Using a magnetic metal detector of Fe thin film with a negligible self-induced torque, the damping-like torque due to Pt/CuOx bilayers is clarified to entirely arise from the spin Hall spin current of the Pt. As the Pt thickness increases, the torque for Fe/Pt/CuOx and Fe/Pt/MgO increases coherently and monotonically, as exactly expected from the spin Hall effect of Pt and the drift-diffusion model of spin angular momentum. These findings suggest poor generality or even universal absence of orbital current torque.

cond-mat.mtrl-sci↗

arXiv2026

Wafer-scale Demonstration of High-voltage beta-Ga2O3 MOSFETs with Excellent Uniformity and over 3kV Breakdown Voltages

This study demonstrates a wafer-scale growth of a 2-inch Si-doped $\beta$-Ga2O3 (100) epitaxial wafer and the realization of uniform, high-voltage lateral $\beta$-Ga2O3 MOSFET arrays. The 2-inch homoepitaxial $\beta$-Ga2O3 (100) film grown by MOCVD exhibit excellent crystalline uniformity with an average rocking curve FWHM of ~27.0 arcsec and a low surface roughness less than 1 nm, alongside a uniform net doping concentration on the value of 4.60 $\times$ 1E17 cm-3. The fabricated MOSFETs deliver a threshold voltage of -31.75 V, a drain-current on/off ratio over 1E9, a specific on-resistance of 126.52 mohm$\cdot$cm2 and breakdown voltage exceeding 3 kV. Statistical analysis across the entire wafer presents good device uniformity, with threshold voltages ranging from -28 V to -36 V, output current densities of 60-75 mA/mm, and a breakdown voltage over 3 kV. These results provide the demonstration using the 2-inch $\beta$-Ga2O3 epitaxial wafer to realize high-voltage $\beta$-Ga2O3 MOSFETs with wafer-scale performance uniformity for next-generation power device application.

cond-mat.mtrl-sci↗

arXiv2026

CityGen: Structure-Guided City-Style Synthesis for Cross-City Autonomous Driving

Autonomous driving systems are commonly trained and evaluated within limited geographic regions, which hinders their scalability when deployed in new cities. However, significant domain shifts in appearance, road topology, and traffic patterns often cause severe performance degradation under cross-city deployment. Existing approaches based on domain adaptation, data augmentation, or synthetic data generation typically rely on labeled target data, city-specific annotations, or task-specific designs, limiting their scalability and effectiveness for holistic evaluation. In this paper, we introduce CityTransfer-Bench, a geographically disjoint benchmark for evaluating cross-city generalization across perception, segmentation, and planning, and propose CityGen, a diffusion-based generative framework that performs zero-label city adaptation via HD-map-conditioned synthesis guided by city-level visual prompts. Extensive experiments demonstrate that CityGen consistently improves cross-city robustness across multiple tasks, establishing a scalable and label-efficient foundation for generalizable autonomous driving.

cs.CV↗

arXiv2026

NVLLM: A 3D NAND-Centric Architecture Enabling Edge on-Device LLM Inference

The rapid growth of LLMs demands high-throughput, memory-capacity-intensive inference on resource-constrained edge devices, where single-batch decoding remains fundamentally memory-bound. Existing out-of-core GPU-based and SSD-like accelerators are limited by DRAM-bound weight movement and inefficient storage access granularity. We present NVLLM, a 3D NAND-centric inference architecture that offloads feed-forward network (FFN) computation into the Flash while executing attention on lightweight CMOS logic with external DRAM. Through wafer-to-wafer stacking, NVLLM tightly integrates multi-plane 3D NAND with compute pipelines, error correction code (ECC) units, and buffers, enabling page-level FFN weight access without DRAM traversal. All GEMM/GEMV operations are decomposed into dot-product primitives executed by out-of-order PE lanes, operating directly on raw NAND reads with integrated ECC. Attention weights remain in DRAM, and a KV-cache-aware scheduler sustains throughput as the context length grows. Evaluated on OPT and LLaMA models with up to 30B parameters, NVLLM achieves a 16.7$\times$--37.9$\times$ speedup over A800-based out-of-core inference and up to 4.7$\times$ speedup over SSD-like designs, with only 2.7\% CMOS area overhead.

cs.AR↗

arXiv2025

Evidence for strong localization of orbital polarization

Whether orbital polarization propagates has become the most essential question of the blooming orbitronics that aims to generate non-local orbital torque and orbital pumping. Recent theories have suggested a strong orbital Hall effect within the light metal Al and a strong orbital Rashba effect at Co/Al interfaces, providing ideal platforms for experimental verification of possible orbital transport effects. Here, we report robust experimental evidence for the strong localization of orbital polarization. We demonstrate that neither the bulk nor the interface of the Al contributes a detectable orbital torque on adjacent magnetic layer with strong bulk and interfacial spin-orbit coupling necessary for potential orbital-spin conversion. These results have clarified that orbital polarization undergoes much faster relaxation than spin polarization and hardly participates in non-local accumulation, transport, or torque generation. The experimental evidence for strong localization of orbital polarization represents a groundbreaking advance towards solving the essential orbital torque debate.

cond-mat.mes-hall↗

arXiv2025

Long Coalition Leads to Shrink? The Roles of Tipping and Technology-Sharing in Climate Clubs

Global cooperation is posited as a pivotal solution to address climate change, yet significant barriers, like free-riding, hinder its realization. This paper develops a dynamic game-theoretic model to analyze the stability of coalitions under multiple stochastic climate tippings, and a technology-sharing mechanism is designed in the model to combat free-ridings. Our results reveal that coalitions tend to shrink over time as temperatures rise, owing to potential free-ridings, despite a large size of initial coalition. The threat of climate tipping reduces the size of stable coalitions compared to the case where tipping is ignored. However, at post-tipping period, coalitions temporarily expand as regions respond to the shock, though this cooperation is short-lived and followed by further shrink. Notably, technology-sharing generates greater collective benefits than sanctions, suggesting that the proposed dynamic technology-sharing pathway bolsters coalition resilience against free-riding while limiting the global warming. This framework highlights the critical role of technology-sharing in fostering long-term climate cooperation under climate tipping uncertainties.

econ.GN↗

arXiv2024

Linear Enhancement of Spin-Orbit Torques and Absence of Bulk Rashba-Type Spin Splitting in Perpendicularly Magnetized [Pt/Co/W]n Superlattices

The development of magnetic heterostructures with strong spin-orbit torques (SOTs), low impedance, strong perpendicular magnetic anisotropy (PMA), and good integration compatibility at the same time is central for high-performance spintronic memory and computing applications. Here, we report the development of the symmetry-broken spin-orbit superlattice [Pt/Co/W]n that can be sputtered-deposited on commercial oxidized silicon substrates and have giant SOTs, strong uniaxial PMA of 9.2 Merg/cm3. The dampinglike and fieldlike SOTs of the [Pt/Co/W]n superlattices exhibit a linear increase with the repeat number n and reach the giant values of 225% and -33% (two orders of magnitude greater than that in clean-limit Pt) at n = 12, respectively. The dampinglike SOT is also of the opposite sign and much greater in magnitude than the fieldlike SOT, regardless of the number of n. These results clarify that the spin current that generates SOTs in the [Pt/Co/W]n superlattices arises predominantly from the spin Hall effect rather than bulk Rashba-type spin splitting, providing a unified understanding of the SOTs in the superlattices. We also demonstrate deterministic switching in thicker-than-50-nm PMA [Pt/Co/W]12 superlattices at a low current density. This work establishes the [Pt/Co/W]n superlattice as a compelling material candidate for ultra-fast, low-power, long-retention nonvolatile spintronic memory and computing technologies.

cond-mat.mtrl-sci↗