Electron-phonon interaction in magic-angle twisted bilayer graphene

Young Woo Choi, Hyoung Joon Choi

Published 2018-09-22Version 1

We study the electron-phonon interaction in magic-angle twisted bilayer graphene (MA-TBG) at the atomistic level, considering the effects of lattice relaxations on the electronic structure. The electron-phonon matrix elements are calculated from the modulation of hopping energy due to atomic displacements of phonon modes. While our method confirms small values of the electron-phonon coupling strength lambda ~ 0.1 in monolayer and unrotated bilayer graphene, our calculated values of lambda for MA-TBG reach over 1 near the half-filling energies of the flat bands. The enhancement is due to the large electron density of states of the flat bands. The lattice relaxation brings significant electron-hole asymmetry in the electronic density of states, thus the hole-side flat bands have much stronger coupling strength than the electron-side. The electron-phonon coupling is nearly isotropic, very weakly dependent on electron momentum. Our results highlight that the electron-phonon coupling in MA-TBG is strong enough to contribute to rich physics of the system.