Arnoldi B, Zachritz S L, Hedwig S, Aeschlimann M, Monti O L A, Stadtmüller B
Department of Physics and Research Center OPTIMAS, Rheinland-Pfälzische Technische Universität Kaiserslautern-Landau, Erwin-Schroedinger-Strasse 46, Kaiserslautern, 67663, Germany.
Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721, USA.
Nat Commun. 2024 Apr 27;15(1):3573. doi: 10.1038/s41467-024-47821-4.
One of the key challenges for spintronic and quantum technologies is to achieve active control of the spin angular momentum of electrons in nanoscale materials on ultrafast, femtosecond timescales. While conventional ferromagnetic materials and materials supporting spin texture suffer both from conceptional limitations in miniaturization and inefficiency of optical and electronic manipulation, non-magnetic centrosymmetric layered materials with hidden spin polarization may offer an alternative pathway to manipulate the spin degree of freedom by external stimuli. Here we demonstrate an approach for generating transient spin polarization on a femtosecond timescale in the otherwise spin-unpolarized band structure of the centrosymmetric 2H-stacked group VI transition metal dichalcogenide WSe. Using ultrafast optical excitation of a fullerene layer grown on top of WSe, we trigger an ultrafast interlayer electron transfer from the fullerene layer into the WSe crystal. The resulting transient charging of the C/WSe interface leads to a substantial interfacial electric field that by means of spin-layer-valley locking ultimately creates ultrafast spin polarization without the need of an external magnetic field. Our findings open a novel pathway for true optical engineering of spin functionalities such as the sub-picosecond generation and manipulation of ultrafast spin currents in 2D heterostructures.
自旋电子学和量子技术面临的关键挑战之一是在飞秒级超快时间尺度上实现对纳米级材料中电子自旋角动量的主动控制。传统的铁磁材料和支持自旋纹理的材料在小型化方面存在概念上的局限性，并且光学和电子操纵效率低下，而具有隐藏自旋极化的非磁性中心对称层状材料可能提供一条通过外部刺激来操纵自旋自由度的替代途径。在此，我们展示了一种在中心对称的2H堆叠的VI族过渡金属二硫属化物WSe原本无自旋极化的能带结构中，在飞秒时间尺度上产生瞬态自旋极化的方法。通过对生长在WSe顶部的富勒烯层进行超快光学激发，我们触发了从富勒烯层到WSe晶体的超快层间电子转移。C/WSe界面产生的瞬态电荷导致了一个强大的界面电场，该电场通过自旋 - 层 - 谷锁定最终在无需外部磁场的情况下产生超快自旋极化。我们的发现为自旋功能的真正光学工程开辟了一条新途径，例如在二维异质结构中产生亚皮秒级超快自旋电流并对其进行操纵。
