Berry phase and traversal time in asymmetric graphene structures

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 Schrödinger-type electrons in contacts, so that the Berry phase and traversal time behavior in contacted and non-contacted graphene differ significantly.

► The Berry phase in asymmetric graphene structures behaves differently than in semiconductors. ► The same result holds for the traversal time in non-contacted or contacted graphene structures. ► The reason is the Dirac evolution law of carriers in graphene, which introduces a new asymmetry type. ► The Dirac equation symmetry in graphene is broken by the Schrödinger electrons in contacts.