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 ABA-stacked 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.

Keywords: Graphene, Angle-resolved photoemission spectroscopy, Berry phase, Tight-binding formalism