Unusual magnetotransport in twisted bilayer graphene from strain-induced open Fermi surfaces

Uniaxial heterostrain in twisted bilayer graphene can have a profound effect on the bandstructure. In this talk, we will discuss the effects of strain in a twisted bilayer graphene device with a twist angle slightly above the magic angle as seen in both theory and transport. Features such as a non-saturating magnetoresistance are well described by our addition of uniaxial heterostrain into the Bistritzer-MacDonald model. We find that strain breaks the degeneracy of the three van Hove points, leading to broad range of densities where open Fermi surfaces exists, explaining the non-saturating magnetoresistance. Additionally, our theory also predicts a marked rotation of the electrical transport principal axes as a function of filling even for fixed strain and for rigid bands. Our results indicate that strain-induced effects may lead to similar phenomenology as interaction-induced nematic order.