The Waterloo Institute for Nanotechnology (WIN) presents a Distinguished Lecture by Professor Kang L. Wang, Distinguished Professor and Raytheon Chair Professor in Physical Science and Electronics in the Electrical Engineering Department of the University of California, Los Angeles (UCLA), United States.
Spin-Orbitronics for Energy Efficient Systems
Energy dissipation has become the major challenge for the current electronics. This is due to the leakage current and the voltage scaling limit of nanoscale structures. With nonvolatile magnetic memory and alike, the leakage current may be minimized and the voltage scaling can be further advanced due to the collective behavior of magnetism. Meanwhile, spin-orbit coupling (SOC), a relativistic effect which describes the coupling between the orbital and spin degrees of freedom, has become the spotlight in the field dubbed as spin-orbitronics.
In continuing effort to resolve these challenges, I will first discuss the engineering of interface SOC to illustrate the efficient control of magnetic memory, in addition to the present approach of channel and tunneling barrier engineering. The engineering of SOC results in the electric field control of magnetic moment or magneto-electric (ME) effect, which results in orders of magnitude lower energy dissipation compared with the current spin transfer torque memory (STTRAM). Likewise, the 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 spin-momentum lock, topological insulators (TIs) are expected to be promising candidates for exploring spin-orbit torque (SOT)-related physics. I will show magnetization switching in a chromium-doped magnetic TI bilayer heterostructure by charge current. A giant SOT of more than three orders of magnitude larger than those reported in heavy metals is also obtained. The integration of these types of spintronics devices with CMOS may resolve the two major limits and nanoarchitectures incorporating these memory devices for intelligent systems will be discussed. This large SOT deriving from the spin-momentum locked surface states of TI may be used to improve the energy efficiency for other applications.
Professor Kang L. Wang
Kang L. Wang is currently 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 the Editor-in-Chief of IEEE TNANO as well as the Editors of Artech House and other publications. His research areas include nanoscale physics and materials, topological insulators, and, spintronics and devices.
*The work was in part supported by ERFC-SHINES, ARO, TANMS, and FAME
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