Nonlocal Spin Dynamics in the Crossover from Diffusive to Ballistic Transport.

Marc Vila,Aron W Cummings,Stephan Roche,Jose H Garcia,Xavier Waintal,Christoph W Groth,Stephen R Power

doi:10.1103/physrevlett.124.196602

Abstract

Improved fabrication techniques have enabled the possibility of ballistic transport and unprecedented spin manipulation in ultraclean graphene devices. Spin transport in graphene is typically probed in a nonlocal spin valve and is analyzed using spin diffusion theory, but this theory is not necessarily applicable when charge transport becomes ballistic or when the spin diffusion length is exceptionally long. Here, we study these regimes by performing quantum simulations of graphene nonlocal spin valves. We find that conventional spin diffusion theory fails to capture the crossover to the ballistic regime as well as the limit of long spin diffusion length. We show that the latter can be described by an extension of the current theoretical framework. Finally, by covering the whole range of spin dynamics, our study opens a new perspective to predict and scrutinize spin transport in graphene and other two-dimensional material-based ultraclean devices.

Highlights

Since the seminal work of Tombros and co-workers [1], who first measured the long spin diffusion length in graphene nonlocal spin devices, a considerable number of studies have explored how to improve the material quality and the efficiency of spin injection and detection so as to reach the upper limit of spin transport [2,3,4,5,6,7,8,9,10,11]
Spin transport in graphene is typically probed in a nonlocal spin valve and is analyzed using spin diffusion theory, but this theory is not necessarily applicable when charge transport becomes ballistic or when the spin diffusion length is exceptionally long
We study these regimes by performing quantum simulations of graphene nonlocal spin valves

Summary

Introduction

Since the seminal work of Tombros and co-workers [1], who first measured the long spin diffusion length in graphene nonlocal spin devices, a considerable number of studies have explored how to improve the material quality and the efficiency of spin injection and detection so as to reach the upper limit of spin transport [2,3,4,5,6,7,8,9,10,11]. Nonlocal Spin Dynamics in the Crossover from Diffusive to Ballistic Transport

Results

Conclusion