Berry phase shift from 2 $\pi$ to $\pi$ in Bilayer graphene by Li-intercalation and sequential desorption

TL;DR

This study demonstrates that Li-intercalation and desorption alter the stacking order of bilayer graphene, changing its Berry phase from 2π to π and significantly increasing its electronic mobility.

Contribution

It reveals a method to control the Berry phase and electronic properties of bilayer graphene through Li-intercalation and desorption, indicating a stacking structure transition.

Findings

Berry phase shifts from 2π to π after Li-intercalation and desorption

Mobility increases fourfold to ~8,000 cm²/V·s

Change from A-B to A-A stacking structure inferred

Abstract

We have found that the Berry phase of bilayer graphene becomes from 2$\pi$ estimated by Shubnikov-de Haas oscillations when the A-B stacked pristine bilayer graphene experiences the Li-intercalation and sequential Li-desorption process in ultrahigh vacuum. Furthermore, the mobility of such processed bilayer graphene increases around four times larger, ~ 8,000 cm2/V$\cdot$s, than that of the pristine bilayer graphene. This is mainly due to increment of the scattering time and decrement of the cyclotron mass, which can be interpreted as a result of the change of the stacking structure of bilayer graphene from A-B to A-A, corresponding to a change from the parabolic to the linear band dispersion.