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船戸 匠*; 加藤 岳生*; 松尾 衛
Physical Review B, 106(14), p.144418_1 - 144418_10, 2022/10
被引用回数：3 パーセンタイル：45.85(Materials Science, Multidisciplinary)We study spin pumping into an anisotropic Dirac electron system induced by microwave irradiation to an adjacent ferromagnetic insulator theoretically. We formulate the Gilbert damping enhancement due to the spin current flowing into the Dirac electron system using second-order perturbation with respect to the interfacial exchange coupling. As an illustration, we consider the anisotropic Dirac system realized in bismuth to show that the Gilbert damping varies according to the magnetization direction in the ferromagnetic insulator. Our results indicate that this setup can provide helpful information on the anisotropy of the Dirac electron system.
大湊 友也*; 大上 能悟*; 松尾 衛
Physical Review B, 105(19), p.195409_1 - 195409_9, 2022/05
被引用回数：1 パーセンタイル：15.88(Materials Science, Multidisciplinary)Angular momentum conversion between mechanical rotation and the valley degree of freedom in 2D Dirac materials is investigated theoretically. Coupling between the valley and vorticity of dynamic lattice distortions is derived by applying the 
method to 2D Dirac materials with an inertial effect. Lattice strain effects are also incorporated. Valley transfer and valley-dependent carrier localization are predicted using the dynamic lattice distortions. The transport properties are found to be controllable, allowing the system to be insulating and to generate pulsed charge current. Our formalism offers a route toward mechanical manipulation of valley dynamics in 2D Dirac materials.
Se
ultrathin films on van der Waals ferromagnet CrSiTe
加藤 剛臣*; 菅原 克明*; 伊東 直洋*; 山内 邦彦*; 佐藤 匠*; 小口 多美夫*; 高橋 隆*; 塩見 雄毅*; 齊藤 英治; 佐藤 宇史*
Physical Review Materials (Internet), 4(8), p.084202_1 - 084202_6, 2020/08
被引用回数：4 パーセンタイル：20.11(Materials Science, Multidisciplinary)We investigated the Dirac-cone state and its modulation when an ultrathin film of topological insulator BiSe was epitaxially grown on a van der Waals ferromagnet CrSiTe (CST) by angle-resolved photoemission spectroscopy. We observed a gapless Dirac-cone surface state in six quintuple-layer (6QL) BiSe on CST, whereas the Dirac cone exhibits a gap of 0.37 eV in its 2QL counterpart. Intriguingly, this gap is much larger than those for BiSe films on Si(111). We also revealed no discernible change in the gap magnitude across the ferromagnetic transition of CST, suggesting the very small characteristic length and energy scale of the magnetic proximity effect. The present results suggest a crucial role of interfacial coupling for modulating Dirac electrons in topological-insulator hybrids.
渡邊 成*; 荒木 康史; 野村 健太郎*
no journal, ,
本研究ではカゴメ電子系のハミルトニアンが持つ微視的性質から、スピン系の巨視的な磁気秩序の性質を導くことを目標に研究を行なった。具体的にはRashba型、及びKane-Mele型のスピン軌道相互作用が存在する単層カゴメ格子上の電子系から出発し、種々の磁気構造における電子系のエネルギーを計算した。これにより基底状態として実現する磁気構造の相図を得た。これによりnoncollinearな磁気秩序が基底状態となることを明らかにした。さらに古典的Heisenberg模型を用いて、スピン間相互作用とジャロシンスキー・守谷相互作用の、電子系のパラメーター依存性を導くことで、古典的Heisenberg模型で記述されるスピン系の巨視的性質を電子系の微視的性質から導いた。
