Year: 2026
Type: preprint
Abstract: 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 $k_BT$.
Source: arXiv (Cornell University)
Language: English
Subfield: Condensed Matter Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: National Science Foundation, U.S. Department of Energy, University of Washington, Office of the Director of National Intelligence, European Commission, Ministry of Education, Culture, Sports, Science and Technology, University of Tokyo, Canada First Research Excellence Fund, Oak Ridge Institute for Science and Education, Intelligence Community Postdoctoral Research Fellowship Program, Materials Research Science and Engineering Center, Harvard University, Natural Sciences and Engineering Research Council of Canada, Japan Society for the Promotion of Science, Division of Materials Research, Basic Energy Sciences
Awards: G1303591526, CAREER: Tunable topological states in twisted van der Waals heterostructures, G2294571178, G2442584775, G2446960435, G4162329948, G4515799968, G4722835768, G4806815962, MRSEC: UW Molecular Engineering Materials Center, G6711204355, G7842812455, G8862470763, G898758523, CAREER: Correlated Phases and Non-equilibrium Dynamics in Topological Flat bands
OpenAlex ID: W7204443367