Energy shift and conduction-to-valence band transition mediated by a time dependent potential barrier in graphene

TL;DR

This paper studies how a time-dependent potential barrier in graphene affects electron energy and band transition, revealing energy gain or loss depending on the barrier's rate of change, and showing electrons can transition to valence band states.

Contribution

It introduces a detailed analysis of energy shifts and band transitions caused by time-dependent barriers in graphene, highlighting the dynamic control of electron states.

Findings

Electrons gain energy after Klein tunneling through a time-dependent barrier.

Negative barrier rate causes electrons to lose energy and transition to valence band states.

The barrier's time variation can effectively control electron energy and band state transitions.

Abstract

We investigate the scattering of a wave packet describing low-energy electrons in graphene by a time-dependent finite step potential barrier. Our results demonstrate that, after Klein tunneling through the barrier, the electron acquires an extra energy which depends on the rate of change the barrier height in time. If such a rate is negative, the electron loses energy and ends up as a valence band state after leaving the barrier, which effectively behaves as a positively charged quasi-particle