Quantifying the charge carrier interaction in metallic twisted graphene superlattices
Abstract
The mechanism of charge carrier interaction in twisted bilayer graphene (TBG) remains an unresolved problem, where some researchers proposed the dominance of the electron-phonon interaction, while the others showed evidence for electron-electron or electron-magnon interactions. Here we propose to resolve this problem by generalizing the Bloch-Gr\"uneisen equation and using it for the analysis of the temperature dependent resistivity in TBG. It is a well-established theoretical result that the Bloch-Gr\"uneisen equation power-law exponent, n, exhibits exact integer values for certain mechanisms. For instance, n=5 implies the electron-phonon interaction, n=3 is associated with electron-magnon interaction and n=2 applies to the electron-electron interaction. Here we interpret the linear temperature-dependent resistance, widely observed in TBG, as n→1, which implies the quasielastic charge interaction with acoustic phonons. Thus, we fitted TBG resistance curves to the Bloch-Gr\"uneisen equation, where we propose that n is a free-fitting parameter. We found that TBGs have a smoothly varied n-value (ranging from 1.4 to 4.4) depending on the Moir\'e superlattice constant, λ, or the charge carrier concentration. This implies that different mechanisms smoothly transition from one to another. The proposed generalized Bloch-Gr\"uneisen equation is applicable to a wide range of problems, including the Earth geology.