[Icqm_seminar] ：Transient spin phenomena at topological insulator/magnetic insulator interfaces

報告題目： Transient spin phenomena at topological insulator/magnetic insulator interfaces 報告人： Nitin Samarth 報告時間： 2013年7月8日（周一）下午4:00 報告地點：理科五号樓607會議室摘要： Contemporary interest in the consequences of breaking time reversal symmetry in 3D topological insulators has prompted intense exploration of physical phenomena at the interface between magnetism and topological insulators. In this context, we have undertaken the study of a variety of epitaxial sample geometries wherein magnetic materials are integrated with 3D topological insulators. For instance, spin- and angle-resolved photoemission measurements of magnetically-doped Bi2Se3 thin films have shown signatures of a magnetically-induced suppression of the spectral weight at the Dirac point, accompanied by a a tunable Berry phase and hedgehog spin texture [1]. Measurements of quantum corrections to the conductivity in such samples and in ferromagnetic insulator/topological insulator bilayers are also consistent with a magnetically induced gap [2,3]. More surprising, we find evidence for a pronounced transient hysteresis in the low temperature magnetoresistance in such samples. These observations seem to be generic to any 3D topological insulator which is interfaced with local moments. This talk will provide an empirical description of these transient spin phenomena and discuss their possible origin, In particular, by measuring electrically gated ferromagnetic insulator/topological insulator bilayers, we show that the transient hysteresis arises from a phonon bottleneck that allows efficient heating of Dirac electrons when local moments are reversed.
1. Su-Yang Xu et al., Nature Physics 8, 616-622 (2012).
2. Duming Zhang et al., Phys. Rev. B 86, 206127 (2012).
3. A. Kandala et al., arxiv:1212.1225
4. A. Kandala et al., in preparation. About the speaker: Nitin Samarth is Downsbrough Department Head and Professor of Physics at The Pennsylvania State University. He completed his undergraduate education in physics at the Indian Institute of Technology (Mumbai) and received a Ph.D. in physics from Purdue University. He joined Penn State University after postdoctoral research at the University of Notre Dame. His research centers on the synthesis and study of semiconductor, magnetic and topological insulator quantum structures with a view towards applications in spintronics and quantum information. His group has particular interest in understanding the transport and dynamics of spins in semiconductors at length scales ranging from the nanoscale to the mesoscopic. Professor Samarth is Fellow of the American Physical Society and the American Association for the Advancement of the Sciences. He has also received the Faculty Scholar Medal in Physical Sciences and the George Atherton Award for Teaching Excellence from Penn State University, and the Outstanding Physics Alumnus Award from Purdue University.