Tuan Dinh Van, Ortmann Frank, Cummings Aron W, Soriano David, Roche Stephan
Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The Barcelona Institute of Science and Technology, Campus UAB, Bellaterra, 08193 Barcelona, Spain.
Institute for Materials Science, Dresden Center for Computational Materials Science, Technische Universität Dresden, 01062 Dresden, Germany.
Sci Rep. 2016 Feb 15;6:21046. doi: 10.1038/srep21046.
The understanding of spin dynamics and relaxation mechanisms in clean graphene, and the upper time and length scales on which spin devices can operate, are prerequisites to realizing graphene-based spintronic technologies. Here we theoretically reveal the nature of fundamental spin relaxation mechanisms in clean graphene on different substrates with Rashba spin-orbit fields as low as a few tens of μeV. Spin lifetimes ranging from 50 picoseconds up to several nanoseconds are found to be dictated by substrate-induced electron-hole characteristics. A crossover in the spin relaxation mechanism from a Dyakonov-Perel type for SiO2 substrates to a broadening-induced dephasing for hBN substrates is described. The energy dependence of spin lifetimes, their ratio for spins pointing out-of-plane and in-plane, and the scaling with disorder provide a global picture about spin dynamics and relaxation in ultraclean graphene in the presence of electron-hole puddles.
理解清洁石墨烯中的自旋动力学和弛豫机制，以及自旋器件能够运行的时间和长度上限，是实现基于石墨烯的自旋电子技术的先决条件。在此，我们从理论上揭示了在具有低至几十微电子伏特的Rashba自旋轨道场的不同衬底上的清洁石墨烯中基本自旋弛豫机制的本质。发现自旋寿命从50皮秒到几纳秒不等，这由衬底诱导的电子 - 空穴特性决定。描述了自旋弛豫机制从SiO2衬底的Dyakonov - Perel型到hBN衬底的展宽诱导退相的转变。自旋寿命的能量依赖性、自旋平面外和平面内指向的比例以及与无序的标度关系，提供了在存在电子 - 空穴 puddles的超清洁石墨烯中自旋动力学和弛豫的全局图景。
