- [BK21] 초청세미나 [9/21] Topological spintronics
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Y-BASE System Semiconductor 그룹 안종현 교수님께서 아래와 같이 초청 세미나를 개최하오니 많은 참여 부탁드립니다.
◎ 일시: 2022년 9월 21일(수) 오전 11시◎ 장소: 연세대학교 백양누리 라제건홀◎ 제목: Topological spintronics
◎ 연사: Hyunsoo Yang / National University of Singapore
◎ 초청: 전기전자공학과 안종현 교수
Layered topological materials such as topological insulators (TIs) and Weyl semimetals are a new class of quantum matters with large spin-orbit coupling. We reveal spin textures of such materials using the bilinear magneto-electric resistance (BMR), which depends on the relative orientation of the current with respect to crystallographic axes [1,2]. These findings open a new branch in spintronics, which discusses the nonlinear transport effects in spin-polarized nonmagnetic materials, applicable to frequency doubling  and energy harvesting applications .
We also visualize current-induced spin accumulation in topological insulators using photocurrent mapping . Topological surface states (TSS) dominated spin orbit torques are identified in Bi2Se3, and magnetization switching at room temperature using Bi2Se3 as a spin current source is demonstrated . In order to tackle current shunting issues in TI, we propose two approaches. Weyl semimetals have a larger conductivity compared to TIs and they can generate a strong spin current from their bulk states. We show the current-driven magnetization switching in WTe2/NiFe with a low power . The current shunting issue can be also overcome by the magnon-mediated spin torque, in which the angular momentum is carried by precessing spins rather than moving electrons. Magnon-torque-driven magnetization switching is demonstrated in the Bi2Se3/NiO/Py devices at room temperature . By injecting the electric current to an adjacent Bi2Se3 layer, spin currents were converted to magnon torques through an antiferromagnetic insulator NiO. The results will invigorate magnon-based memory and logic devices, which is relevant to the energy-efficient control of spin devices .
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