Electronic transport in BN-encasulated graphene limited by remote phonon scattering

TL;DR

This study reveals that remote phonon scattering from BN's out-of-plane phonons significantly limits electrical transport in hBN-encapsulated graphene, especially at room temperature and low carrier densities.

Contribution

It combines experiments and ab initio calculations to clarify the role of BN's phonons in graphene resistivity, resolving a longstanding debate.

Findings

BN's out-of-plane phonons strongly influence resistivity between 150 K and room temperature.

Higher-energy LO modes and intrinsic graphene phonons cannot fully explain the observed resistivity trends.

Remote phonon scattering becomes more significant at low carrier densities due to reduced screening.

Abstract

We study the impact of BN's phonons on the electrical resistivity of hBN-encapsulated graphene. While encapsulation yields high-mobility devices, the surrounding BN itself introduces remote scattering from polar optical phonons, whose role in standard resistivity measurements remains unclear. We combine high-quality transport experiments with ab initio calculations including a proper treatment of dynamically screened remote interactions. We demonstrate that hBN's out-of-plane phonons strongly influence resistivity between 150 K and room temperature, whereas higher-energy LO modes and intrinsic graphene phonons alone cannot explain the observed trends. The coupling between electrons and the BN's phonons becomes more pronounced at low carrier densities due to reduced screening. Our findings establish that remote phonon scattering fundamentally limits transport in encapsulated graphene, solving a longstanding debate.