Raman bands of twisted bilayer graphene

A theoretical approach to the modelling of the resonant Raman scattering by phonons in twisted bilayer graphene is developed and presented. The normally very large unit cells of twisted bilayer graphene hinder the large scale calculation of the electronic, vibrational, and optical properties by microscopic models. Here, a perturbative approach within a non-orthogonal tight-binding model is proposed that allows for a significant reduction of the computational time for such calculations. This approach is applied to the electronic band structure, electronic density of states, dielectric function, and Raman excitation profile of the most intense first-order Raman band - the G band - for twisted bilayer graphene with up to a few hundred carbon atoms in the unit cell. The computational scheme can easily be extended to second-order Raman bands of twisted bilayer graphene as well. The obtained theoretical predictions can be used for characterization of twisted bilayer graphene samples, using experimental Raman data. Copyright (c) 2017 John Wiley & Sons, Ltd.