Long-distance spin transport through a graphene quantum Hall antiferromagnet

• DOI: 10.1038/s41567-018-0161-5
• Publication Date: 2018-06-08T14:24:50Z
• Authors: Petr Stepanov; Shi Che; Dmitry Shcherbakov; Jiawei Yang; Ruoyu Chen; Kevin Thilahar; Greyson Voigt; Marc W. Bockrath; Dmitry Smirnov; Kenji Watanabe; Takashi Taniguchi; Roger K. Lake; Yafis Barlas; Allan H. MacDonald; Chun Ning Lau
• Keywords: Condensed Matter - Materials Science; Condensed Matter - Mesoscale and Nanoscale Physics; Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Materials Science (cond-mat.mtrl-sci); FOS: Physical sciences; 7. Clean energy

Antiferromagnetic insulators (AFMI) are robust against stray fields, and their intrinsic dynamics could enable ultrafast magneto-optics and ultrascaled magnetic information processing. Low dissipation, long distance spin transport and electrical manipulation of antiferromagnetic order are much sought-after goals of spintronics research. Here, we report the first experimental evidence of robust long-distance spin transport through an AFMI, in our case the gate-controlled, canted antiferromagnetic (CAF) state that appears at the charge neutrality point of graphene in the presence of an external magnetic field. Utilizing gate-controlled quantum Hall (QH) edge states as spin-dependent injectors and detectors, we observe large, non-local electrical signals across a 5 micron-long, insulating channel only when it is biased into the nu=0 CAF state. Among possible transport mechanisms, spin superfluidity in an antiferromagnetic state gives the most consistent interpretation of the non-local signal's dependence on magnetic field, temperature and filling factors. This work also demonstrates that graphene in the QH regime is a powerful model system for fundamental studies of antiferromagnetic, and in the case of a large in-plane field, ferromagnetic spintronics.