Spin precession has been used to measure the transmission time \tau over a distance L in a graphene sheet. Since conduction electrons in graphene have an energy-independent velocity v, one would expect \tau > L/v. Here we calculate that \tau < L/v at the Dirac point (= charge neutrality point) in a clean graphene sheet, and we interpret this result as a manifestation of the Hartman effect (apparent superluminality) known from optics.
@article{arxiv.0910.2657,
title = {Hartman effect and spin precession in graphene},
author = {R. A. Sepkhanov and M. V. Medvedyeva and C. W. J. Beenakker},
journal= {arXiv preprint arXiv:0910.2657},
year = {2009}
}
Comments
6 pages, 4 figures; v2: added a section on the case of perpendicularly aligned magnetizations; v3: added a figure