Strong intervalley scattering in twisted bilayer graphene revealed by high-temperature magnetooscillations

Superlattice-induced modulation of two-dimensional materials can give rise to a host of surprising yet counter-intuitive effects and impact electron transport in a variety of non-trivial ways. Twisted bilayer graphene (TBG) provides an exceptional platform in which to study these superlattice-enabled transport effects, as exemplified by numerous experiments revealing many intriguing interaction-driven phenomena in this system [1]. Integral to understanding transport properties of TBG systems is a knowledge of the electron scattering mechanisms that govern momentum relaxation in the superlattice. We show that at small twist angles, unlike in monolayer graphene, intervalley electron scattering plays a critical role in momentum relaxation. This scattering process reveals itself in high-temperature magnetooscillations [2], which allow us to estimate the intervalley scattering rate and determine the quasiparticle lifetime in small-angle TBG.

[1] E. Andrei and A. MacDonald, arXiv.2008.08129 (2020).
[2] I. A. Dmitriev et al., Rev. Mod. Phys. 84, 1709 (2012).