Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
田島 裕之*; 大上 能悟*; 松尾 衛
Physical Review A, 106(3), p.033310_1 - 033310_8, 2022/09
被引用回数：3 パーセンタイル：23.32(Optics)We elucidate the multiparticle transport of pair tunneling and spin tunneling in strongly correlated interfaces. Not only usual single-particle tunneling but also interaction-induced multiparticle tunneling processes naturally arise from a conventional microscopic model without any empirical parameters, through the overlap of the many-body wave functions around the interface. We demonstrate how anomalous tunneling currents occur in a strongly interacting system due to the pair-tunneling process which we derived microscopically. Our formulation is useful for junction systems in various disciplines, including atomtronics, spintronics, and nuclear reactions.
荒木 康史; 三澤 貴宏*; 野村 健太郎*
Physical Review Research (Internet), 3(2), p.023219_1 - 023219_15, 2021/06
本論文では、トポロジカルディラック半金属(TDSM)表面のギャップレス状態を介した、長距離スピン伝送を理論面から提案する。次世代のスピントロニクス素子の構築のためには、散逸の少ないスピン流を実現することが必要である。主要なスピン流のキャリアは金属中の伝導電子や磁性絶縁体中のスピン波であるが、これらはジュール熱やギルバート緩和により伝播距離が制限される問題がある。本研究ではTDSM(Cd
As
, NaBi等)のスピン・ヘリカルな表面状態が、乱れに対して頑強である性質を用いて、低散逸で長距離のスピン輸送を提案する。2つの磁性絶縁体とTDSMの接合系を考え、一方の磁性体の磁化ダイナミクスにより、TDSM表面を介して他方の磁性体に注入されるスピン流に注目する。表面における輸送理論と、格子模型による実時間発展シミュレーションを併用することにより、TDSM表面を流れるスピン流は準量子化された値をとり、その値は界面の微視的な結合の構造によらないことを示す。さらに、このスピン流は長距離においても乱れに対して強いことを示し、TDSMがスピントロニクス素子へ応用可能な表面状態をもつことを提案する。
O thin filmsQin, J.*; Hou, D.*; Chen, Y.*; 齊藤 英治; Jin, X.*
Journal of Magnetism and Magnetic Materials, 501, p.166362_1 - 166362_4, 2020/05
被引用回数：4 パーセンタイル：26.39(Materials Science, Multidisciplinary)Spin transmission in CrO films of different crystalline textures is studied experimentally. With YFe
O
/CrO/Pt trilayer devices, a spin current is injected into CrO by spin pumping from YFeO, and the spin transmission is monitored by the inverse spin Hall voltage (
) in Pt. For (0001) plane textured CrO films, vanishes quickly below the N
el temperature. However, the shows a broad shoulder below the Nel temperature for 
and 
plane co-textured CrO. Such a difference in the temperature dependence of CrO can be understood by the different Nel vector orientations with respect to the injected spin moment direction.
Hou, D.*; Qiu, Z.*; 齊藤 英治
NPG Asia Materials, 11, p.35_1 - 35_6, 2019/07
被引用回数：40 パーセンタイル：84.83(Materials Science, Multidisciplinary)Spin transport is a key process in the operation of spin-based devices that has been the focus of spintronics research for the last two decades. Conductive materials, such as semiconductors and metals, in which the spin transport relies on electron diffusion, have been employed as the channels for spin transport in most studies. Due to the absence of conduction electrons, the potential to be a spin channel has long been neglected for insulators. However, since the demonstration of spin transmission through a ferromagnetic insulator, it was realized that insulators with magnetic ordering can also serve as channels for spin transport. Here, the recent progress of spin transport in antiferromagnetic insulators is briefly described with an introduction to the experimental techniques. The observations regarding the temperature dependence of spin transmission, spin current switching and the negative spin Hall magnetoresistance are discussed. We also include the challenges for developing the functionality of antiferromagnetic insulators as well as the unresolved problems from the experimental observations.
荒木 康史; 三澤 貴宏*; 野村 健太郎*
no journal, ,
Cd
As
等のトポロジカルディラック半金属の表面には、フェルミアークとしてスピンヘリカルな1次元的状態が存在する。本講演ではこの表面状態を介したスピン輸送について議論する。半金属表面に2つの磁性絶縁体が接合した状況を考え、片方の磁性体の磁化ダイナミクスが、半金属表面状態を介して他方の磁性体に与えるスピン流を扱う。このスピン流がフェルミアークの長さに応じた量子化値をとることを、解析的および数値的に示す。
荒木 康史
no journal, ,
Spin current, namely the flow of spin angular momentum carried by electrons or spin waves in materials, plays the key role in designing next-generation spintronics devices. For efficient use of spin current, we need to lower the energy dissipation in the conversion process between charge and spin currents, and the transmission process of spin current. In this talk, I introduce my recent theoretical works for achieving low-dissipation spin-charge conversion and spin current transmission by making use of topological edge states. In particular, we have considered the roles of helical edge states on two-dimensional (2D) quantum spin Hall insulators (QSHIs) and 3D topological Dirac semimetals (TDSMs), which are (quasi-)1D channels protected by the bulk topology and hence robust against disorder. Helical edge states are suitable for spin-charge conversion and spin current transmission, due to their spin-helical nature, where the electrons propagate in directions depending on their spins (up/down). For spin-charge conversion, we consider spin pumping from a ferromagnet (FM) into a QSHI or a TDSM. The injected spin current is converted into a charge current flowing at the interface, and we evaluate the conversion rate from the spin current to the charge current. As a result, we find that the conversion rate is enhanced under a strong exchange coupling at the interface, around 100 times larger than the conversion rate at 2D interfaces of complex oxides. For spin current transmission, we consider the transmission between two FMs (FM1/FM2) mediated by the helical edge states of a QSHI or a TDSM. We evaluate the spin current injected from FM1 into FM2 analytically and numerically, which exerts a torque on FM2 switching its magnetization. As a result, we find that the spin current is semi-quantized depending on the number of edge channels, and is robustly transmitted against disorder over a long range.
