Wave packet dynamics and valley filter in strained graphene

TL;DR

This paper investigates wavepacket dynamics in strained graphene, demonstrating a valley filter mechanism and analyzing the effects of magnetic fields on zitterbewegung, revealing persistent and transient oscillations depending on field configurations.

Contribution

It introduces an efficient valley filter in strained graphene and analyzes the combined effects of external and strain-induced magnetic fields on wavepacket behavior.

Findings

Valley filter effectively separates K and K' valley components.

External and strain-induced magnetic fields influence zitterbewegung persistence.

Combined fields cause asymmetric wavepacket oscillations in Dirac cones.

Abstract

The time evolution of a wavepacket in strained graphene is studied within the tight-binding model and continuum model. The effect of an external magnetic field, as well as a strain-induced pseudo-magnetic field, on the wave packet trajectories and zitterbewegung are analyzed. Combining the effects of strain with those of an external magnetic field produces an effective magnetic field which is large in one of the Dirac cones, but can be practically zero in the other. We construct an efficient valley filter, where for a propagating incoming wave packet consisting of momenta around the K and K' Dirac points, the outgoing wave packet exhibits momenta in only one of these Dirac points, while the components of the packet that belong to the other Dirac point are reflected due to the Lorentz force. We also found that the zitterbewegung is permanent in time in the presence of either external or strain-induced magnetic fields, but when both the external and strain-induced magnetic fields are present, the zitterbewegung is transient in one of the Dirac cones, whereas in the other cone the wave packet exhibits permanent spatial oscillations.