Spin-orbit-mediated spin relaxation in ballistic graphene materials

Resumen del póster presentado al 1st Workshop Spain-Taiwan: "2D Materials and Interfaces for Spintronics", celebrado en Barcelona (España) del 23 al 25 de octubre de 2017.Graphene is a promising platform for future electronics and spintronics due to its high carrier mobility and low intrinsic spin-orbit coupling. Most of the work on understanding spin relaxation in graphene for spintronic applications relies on the assumption that spin polarization is lost due to scattering and dephasing processes. Here, we present results of a recent theoretical study of spin dynamics of supported graphene in the ballistic regime. The time-dependent spin expectation value is computed numerically for a graphene tight-binding without the presence of disorder, thus providing the time evolution of an initially spin-polarized wave packet in a graphene sheet. The present findings can be relevant in high-quality devices where electron scattering no longer dominates the spin relaxation because in this ballistic regime, there is a lack of theoretical understanding of the spin dynamics. We show that in certain conditions a small spin-orbit coupling induced by a substrate is sufficient to dephase the spin precession and limit the spin lifetime to a few nanoseconds. In addition, the conditions to observe spin transport anisotropy along different transport directions is discussed in this clean limit. Finally, the case of bilayer graphene, strongly debated in the literature, will be considered in order to clarify experimental results.Peer reviewe