Electron dynamics and dynamic localization in asymmetric periodic potentials

We consider the dynamics of electrons in asymmetric periodic potentials in ac electric fields. It is shown that the conditions for dynamic localization are not affected by the asymmetry of the potential and that the same ac field yields dynamic localization for any potential. However, the asymmetry does affect the general dynamics and must be included explicitly in dynamical calculations. We also show that the condition for dynamic localization in any potential can be interpreted as the requirement that the electron spend equal time at every point in the first Brillouin zone.