Berry-phase effect on reflection amplitude in bilayer graphene with potential step

We theoretically study the phase of the reflection amplitude of an electron at a lateral potential step in Bernal-stacked bilayer graphene [1]. The phase shows an 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 gates generating the step, and can be observed in an interferometry setup. \\[4pt] [1] Sunghun Park and H.-S. Sim, Phys. Rev. Lett. 103, 196802 (2009).