Enhanced Phonon-Assisted Tunneling in Metal -- Twisted Bilayer Graphene Junctions

TL;DR

This study uses tunneling spectroscopy to reveal enhanced phonon-assisted electron tunneling in twisted bilayer graphene, highlighting the role of moiré band density of states and phonon modes, advancing understanding of electron-phonon interactions.

Contribution

It demonstrates increased phonon-assisted tunneling in twisted bilayer graphene due to relaxed momentum matching, supported by theoretical phonon dispersion calculations.

Findings

Enhanced phonon-assisted tunneling compared to Bernal bilayer graphene

Identification of low-energy phonon modes in twisted bilayer graphene

Planar tunneling as a tool for studying electron-phonon coupling

Abstract

We report planar tunneling spectroscopy measurements on metal-WSe$_2$-twisted bilayer graphene heterostructures across a broad range of gate and bias voltages. The observed experimental features are attributed to phonon-assisted tunneling and the significantly high density of states within the moir\'e bands. A notable finding is the enhanced phonon-assisted tunneling in twisted bilayer graphene compared to Bernal bilayer graphene, which arises from a more relaxed in-plane momentum matching criterion. Theoretical calculations of phonon dispersions enable us to identify low-energy phonon modes in both Bernal and twisted bilayers of graphene, thereby elucidating the underlying mechanism of tunneling. Our results establish planar tunneling as a versatile tool to further understand electron-phonon coupling in twisted van der Waals materials.