扭曲双层石墨烯中铁-约瑟夫森效应的特征
Signatures of a ferro-Josephson effect in twisted graphene
- Quantum Matter Institute, University of British Columbia（不列颠哥伦比亚大学量子物质研究所）
- Department of Physics and Astronomy, University of British Columbia（不列颠哥伦比亚大学物理与天文学系）
- Department of Physics, Birla Institute of Technology and Science, Pilani, Hyderabad Campus（比拉理工学院皮拉尼校区海得拉巴分校物理系）
- Department of Physics, University of Washington（华盛顿大学物理系）
- Intelligence Community Postdoctoral Research Fellowship Program, University of Washington（华盛顿大学情报界博士后研究奖学金项目）
- Research Center for Electronic and Optical Materials, National Institute for Materials Science（国家材料科学研究所电子与光学材料研究中心）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
研究在扭曲石墨烯范德华异质结构中观测到与铁-约瑟夫森效应一致的特征，其源于自旋畴壁磁矩的电流驱动进动，确立非线性输运可作为探测低能同位旋畴壁动力学的灵敏工具。
AI中文摘要：
当自旋极化电流被驱动穿过磁畴壁时，产生的自旋转移力矩在超过临界阈值后，会使畴壁的磁矩发生进动。这种进动会调制穿过畴壁的电子所经历的贝里曲率，产生一种本质上属于拓扑性质的电动势，其大小与进动频率成正比，恰好对应于直流约瑟夫森效应，因此被命名为铁-约瑟夫森效应。我们在扭曲石墨烯范德华异质结构中报告了与该效应一致的特征，其中自旋和谷纹理通过交换相互作用、洪德耦合以及自旋-轨道相互作用相互关联。当调节至同位简并自发破缺的填充度时，样品在平行磁场$B_\parallel=0$附近不到1毫特的范围内，纵向电阻会出现一个尖锐的峰，且该峰会随电流减小至零而消失。在微分电阻中，该特征会分解为尖锐的共振，这些共振在微特斯拉量级的$B_\parallel$和皮安量级的电流下发生色散。我们认为这些共振源于电流驱动的自旋畴壁磁矩进动，与微小外加场设定的面内各向异性相互竞争，且它们确立了非线性输运作为探测远低于$k_BT$能量尺度下同位旋畴壁动力学的灵敏工具。
英文摘要：
When a spin-polarized current is driven across a magnetic domain wall, the resulting spin-transfer torque may, beyond a critical threshold, set the wall's moments into precession. This precession modulates the Berry curvature experienced by electrons traversing the wall, producing an electromotive force that is topological in nature and proportional to the precession frequency, mapping precisely onto the DC Josephson effect and leading to the name ferro-Josephson effect. We report signatures consistent with this effect in a twisted graphene van der Waals heterostructure, where spin and valley textures are linked by exchange, Hund's coupling, and spin-orbit interactions. Tuned to fillings where the isospin degeneracy is spontaneously broken, the samples develop a sharp peak in the longitudinal resistance within a fraction of a millitesla of $B_\parallel=0$---a peak that disappears as the current is reduced toward zero. In differential resistance the feature resolves into sharp resonances that disperse with $B_\parallel$ on microtesla and picoampere scales. We argue that these arise from the current-driven precession of spin-domain-wall moments, in competition with the in-plane anisotropy set by a minuscule applied field, and that they establish nonlinear transport as a sensitive probe of isospin domain-wall dynamics at energy scales far below $k_BT$.
