Band-Selective Simulation of Photoelectron Intensity and Converging Berry Phase in Trilayer Graphene

The Berry phase is one of the key elements to understand quantum-mechanical phenomena such as the Aharonov-Bohm effect and the unconventional Hall effect in graphene.In monolayer and bilayer graphene the Berry phase has been manifested by an anisotropic distribution of photoelectron intensity along a closed loop in the momentum space as well as its rotation by a characteristic angle upon rotating light polarization.Here we report a band-selective simulation of photoelectron intensity of trilayer graphene to understand its Berry phase within the tight-binding formalism.ABC-and ABA-stacked trilayer graphene show characteristic rotational angles of the photoelectron intensity distribution, as predicted from their well-known Berry phases.Surprisingly, however, in ABA-stacked trilayer graphene, the rotational angle changes upon approaching the band touching point between the conduction and valence bands, suggesting that the Berry phase changes as a function of the binding energy.The binding energy-dependent Berry phase is attributed to enhanced hybridization of the two electron bands of ABAstacked trilayer graphene that merge at the band touching point, resulting in a converging Berry phase.These findings will provide an efficient way of tuning the Berry phase and hence exotic phenomena stemming from the Berry phase.