Speaker: Dr. Wei Han
Affiliation: International Center for Quantum Materials (ICQM), Peking University
Abstract Details: Spintronics aims to use the spin degrees of freedom for future information technologies. Spin orbit Torque, that uses spin currents generated by spin-orbit interactions in non-magnetic heavy metals, has attracted enormous attention due to potential application to development of more powerful spintronic devices. A key challenge for spintronics, especially spin orbit torque, is the efficient generation of spin currents from charge currents. In this talk, I will present our recent results towards more efficient spin and charge conversion. I will first briefly discuss the role of interface transparency for the spin orbit torque at the interface between platinum and a ferromagnetic material [1]. The efficiency of the effective spin orbit torque could be modulated by engineering the interface. Then, I will mainly discuss the potential to use emergent 2D quantum materials for spin and charge conversion since they provide new mechanisms of spin currents generation [2]. The facet-dependent spin Hall effect and spin orbit torque in single crystalline antiferromagnetic IrMn3 will be discussed [3]. This result suggests a novel mechanism of the spin current generation arising from the triangular spin configurations in the single crystalline IrMn3. At the end, I will present the spin to charge conversion in the spin-momentum locked surface states of the topological Kondo insulator (SmB6), of which pure surface states exist at low temperatures [4]. References: [1] Weifeng Zhang*, Wei Han*, Xin Jiang, See-Hun Yang, and Stuart Parkin, Nature Physics 11, 496–502 (2015). [2] Wei Han, APL Materials 4, 032401 (2016). [3] Weifeng Zhang*, Wei Han*, See-hun Yang, Yan Sun, Yang Zhang, Binghai Yan, and Stuart S. P. Parkin, Science Advances, 2: e1600759 (2016). [4] Qi Song, Jian Mi, Dan Zhao, Tang Su, Wei Yuan, Wenyu Xing, Yangyang Chen, Tianyu Wang, Tao Wu, Xian Hui Chen, X. C. Xie, Chi Zhang, Jing Shi, and Wei Han, Nature Communications (In press) (2016).

About The Speaker: Dr. Wei Han has been a tenure-track assistant professor in the International Center for Quantum Materials (ICQM) at Peking University since 2014. After he received his Ph.D. in physics at University of California, Riverside in 2012, Dr. Han spent two and half years at IBM Almaden Research Center as a postdoctoral associate. Dr. Han is the recipient of the 2012 APS GMAG student dissertation award and the 2016 IUPAP Young Scientist Prize in Magnetism (C9). His main research focus has recently been on graphene spintronics, spin orbit torque in magnetic heterostructures, and two-dimensional quantum interfaces/materials. Contact Dr. Wei Han, ICQM, Peking University; Email: weihan@pku.edu.cn Group Page: http://www.phy.pku.edu.cn/~LabSpin/links.html"

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