The Berry phase and the group-velocity-based traversal time have been calculated for an asymmetric non-contacted or contacted graphene structure, and significant differences have been observed compared to semiconductor heterostructures. These differences are related to the specific, Dirac-like evolution law of charge carriers in graphene, which introduces a new type of asymmetry. When contacted with electrodes, the symmetry of the Dirac equation is broken by the Schrodinger-type electrons in contacts, so that the Berry phase and traversal time behavior in contacted and non-contacted graphene differ significantly.
@article{arxiv.1105.5467,
title = {Berry Phase and Traversal Time in Asymmetric Graphene Structures},
author = {Daniela Dragoman},
journal= {arXiv preprint arXiv:1105.5467},
year = {2015}
}