Ville Vierimaa, Zheyong Fan, Ari Harju
Department of Applied Physics, Aalto University, Helsinki, Finland
Graphene has spanned a lot of interest in the field of spintronics because of its small intrinsic spin-orbit coupling (SOC). In theory, the small SOC should lead to long spin relaxation times, allowing spin to carry information efficiently. However, there is a large discrepancy between the experiments and the theory as the measured relaxation times are a few orders of magnitude shorter than predicted.
In this work we have studied the effect of magnetic charged impurities on the spin relaxation in graphene. We model the impurities with Gaussian-shaped potential similar to , with an additional spin-dependent term in the potential. The focus has mostly been on the range of the potential, but the magnitude of the spin-dependent part and concentration of the impurities are also considered.
We found out that while both spin and charge relaxation times decrease with increasing defect size, spin does so faster. Therefore, a small concentration of large puddles is expected to relax spin fast but have minor effect on the charge transport properties. This result is similar to what is observed in the typical experiments and could be used to explain the short observed relaxation times.
 A. Rycerz, J. Tworzydlo, and C. W. J. Beenakker, EPL, 79, 57003 (2007)
Ville Vierimaa is a PhD student at the Department of Applied physics at Aalto University. He is part of the Quantum Many-Body Physics group, led by Ari Harju. He received his MSc from Aalto in early 2016 and is currently working on quantum transport calculations on graphene. The work is focused towards the spin and spin-dependent transport properties.