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

Soni, Radhika; Datta, Suvronil; Bajaj, Robin; Bhowmik, Saisab; Mandal, Shinjan; Suri, Baladitya; Watanabe, Kenji; Taniguchi, Takashi et al. · ACS Nano · 2025

basic_science · Level V

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Abstract

We report planar tunneling spectroscopy measurements on metal-WSe<sub>2</sub>-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 moiré 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.