Bilayer Graphene Interferometry : Phase Jump and Wave Collimation

TL;DR

This paper theoretically investigates the phase behavior of electrons in bilayer graphene at potential steps, revealing a Berry-phase-induced phase jump and proposing an interferometry setup for wave collimation and phase detection.

Contribution

It introduces a novel analysis of phase jumps due to Berry phase effects in bilayer graphene and proposes an interferometry method for wave control.

Findings

Identified a $$ phase jump in reflection amplitude at specific incidence angles.

Demonstrated robustness of the phase jump against band gap variations.

Proposed an interferometry setup for electron wave collimation and phase measurement.

Abstract

We theoretically study the phase of the reflection amplitude of an electron (massive Dirac fermion) at a lateral potential step in Bernal-stacked bilayer graphene. The phase shows anomalous jump of $\pi$, as the electron incidence angle (relative to the normal direction to the step) varies to pass $\pm \pi/4$. The jump is attributed to the Berry phase associated with the pseudospin-1/2 of the electron. This Berry-phase effect is robust against the band gap opening due to the external electric gates generating the step. We propose an interferometry setup in which collimated waves can be generated and tuned. By using the setup, one can identify both the $\pi$ jump and the collimation angle.