▎ 摘　　要

Brillouin zones of graphene systems possess Dirac points, where band degeneracies occur. We study the variety of (and large magnitude of) phases that the electronic states can acquire when a uniform time-dependent electric field carries the electrons around one or more Dirac points in a nonconcentric fashion. An experimentally accessible determination of excess Berry phases is proposed involving the Zitterbewegung of electronic current near an orthogonality point in adiabatic motion.