Topological Spintronics - Dr. Kang L. Wang, University of California, Los Angeles
Spin-orbit coupling (SOC), a relativistic effect that describes the coupling between the orbital and spin degrees of freedom, has become the spotlight in the field dubbed as spin-orbitronics. I will discuss the engineering of interface SOC to illustrate the efficient electric field control of magnetic memory in addition to the present approach of spin tunneling current engineering.
In the presence of electric field, a magnetic moment may be switched with this magneto-electric (ME) effect in SOC heterostructures, which has shown orders of magnitude improvement in energy efficiency compared with the current spin transfer torque memory (STTRAM). Likewise, a large SOC is also shown to give rise to a large spin-orbit torque or SOT. Due to the presence of an intrinsic extraordinarily strong SOC and the spin-momentum lock effect, topological insulators (TIs) are expected to be promising candidates for creating highly an efficient spin-orbit torque (SOT). In TI/ferromagnetic heterostructures, switching in a chromium-doped magnetic TI bilayer heterostructure has been demonstrated by charge current. A giant SOT of more than three orders of magnitude larger than those reported in heavy metals is also obtained. This large SOT driven from the spin-momentum locked surface states of TI may be used to improve the energy efficiency for applications. The control of the interface for different heterostructures by a gate electric potential is demonstrated to enable voltage induced switching. New physics may be learned from TI/antiferromagnet hetero-interfaces. Examples will be discussed.
Kang L. Wang is a Distinguished Professor and holds Raytheon Chair Professor in Physical Science and Electronics in the Electrical Engineering Department of the University of California, Los Angeles (UCLA). He received his BS degree from National Cheng Kung University (Taiwan) and his MS and PhD degrees from the Massachusetts Institute of Technology. He is a Fellow of the IEEE and a member of the American Physical Society. He also served as editor-in-chief of IEEE TNANO, editor of Artech House, consulting editor for Spins, and editor for Science Advances and other publications. His research areas include nanoscale physics and materials; topological insulators; spintronics and devices, nonvolatile electronics and low dissipation devices; molecular beam epitaxy; nanoarchitectures.