Wei Han - Spin Current: a Unique Probe of Quantum Materials

Spin current generally means the electron-mediated current with spin polarization after the discovery of giant and tunneling magnetoresistances in 1980s. Recently, new types of spin current in quantum materials have been found, which are mediated by magnons, quasiparticles in SC, spinons, and spin superfluidity states etc. These quantum materials have exhibited fascinating spin-dependent properties, which are attractive for future spintronics applications [1]. A new direction of using spin current as a probe for quantum materials has been identified. In this talk, I will discuss some primary experimental results to illustrate how spin current could be a powerful probe for new quantum materials. I will discuss the SC quasiparticle-mediated spin current as a probe for spin dynamics of an s-wave superconducting film [2], which might be useful to probe the spin dynamics for unconventional superconducting thin films. I will also discuss the spin superfluid-mediated spin current for the probe of novel quantum phase of spin superfluidity/superconductor ground states. The spin current in canted antiferromagnet Cr2O3 is investigated, which provides important experimental signatures of the spin superfluid ground states [3]. At the end, I will present the current status and my personal outlook of this exciting direction of using spin current as a probe for quantum materials [4]. References [1] W. Han*, Y. Otani, and S. Maekawa, npj Quantum Materials, 3, 27 (2018). [2] Y. Yao, Q. Song, Y. Takamura, J. Cascales, W. Yuan, Y. Ma, Y. Yun, X. C. Xie, J. S. Moodera, and W. Han*, Physical Review B 97, 224414 (2018). [3] W. Yuan, Q. Zhu, T. Su, Y. Yao, W. Xing, Y. Chen, Y. Ma, X. Lin, J. Shi*, R. Shindou, X. C. Xie*, and W. Han*, Science Advances, 4, eeat1098 (2018). [4] W. Han*, S. Maekawa and X. C. Xie, Nature Material (2019); DOI: 10.1038/s41563-0190456-7.