Excess resistivity in graphene superlattices caused by umklapp electron-electron scattering

TL;DR

This paper demonstrates that electron-electron umklapp scattering significantly increases resistivity in graphene superlattices, affecting mobility and showing strong temperature and carrier density dependence, with implications for device design.

Contribution

It provides experimental evidence of umklapp scattering dominating transport in graphene superlattices, a phenomenon previously elusive in experiments.

Findings

Umklapp scattering causes giant excess resistivity.

Resistivity increases rapidly with superlattice period.

Temperature dependence is quadratic with electron-hole asymmetry.

Abstract

Umklapp processes play a fundamental role as the only intrinsic mechanism that allows electrons to transfer momentum to the crystal lattice and, therefore, provide a finite electrical resistance in pure metals. However, umklapp scattering has proven to be elusive in experiment as it is easily obscured by other dissipation mechanisms. Here we show that electron-electron umklapp scattering dominates the transport properties of graphene-on-boron-nitride superlattices over a wide range of temperatures and carrier densities. The umklapp processes cause giant excess resistivity that rapidly increases with increasing the superlattice period and are responsible for deterioration of the room-temperature mobility by more than an order of magnitude as compared to standard, non-superlattice graphene devices. The umklapp scattering exhibits a quadratic temperature dependence accompanied by a pronounced electron-hole asymmetry with the effect being much stronger for holes rather than electrons. Aside from fundamental interest, our results have direct implications for design of possible electronic devices based on heterostructures featuring superlattices.