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제목
[BK21] 초청세미나 [9/21] Topological spintronics
작성일
2022.09.19
작성자
전기전자공학부
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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

◎ Abstract 

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 [3] and energy harvesting applications [4].

We also visualize current-induced spin accumulation in topological insulators using photocurrent mapping [5]. 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 [6]. 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 [7]. 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 [8]. 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 [9].

 

[1] P. He et al., Nat. Phys. 14, 495 (2018)

[2] P. He et al., Nat. Comm. 10, 1290 (2019)

[3] P. He et al., Nat. Comm. 12, 698 (2021)

[4] D. Kumar et al., Nat. Nanotechnol. 16, 421 (2021)

[5] Y. Liu et al., Nat. Comm. 9, 2492 (2018)

[6] Y. Wang et al., Nat. Comm. 8, 1364 (2017)

[7] S. Shi et al., Nat. Nano. 14, 945 (2019)

[8] Y. Wang et al., Science 366, 1125 (2019)

 [9] K. Lee et al., Nat. Nanotechnol. 16, 1337 (2021)