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

R Soni and S Datta and R Bajaj and S Bhowmik and S Mandal and B Suri and K Watanabe and T Taniguchi and M Jain and U Chandni, ACS NANO, 19, 25325-25333 (2025).

DOI: 10.1021/acsnano.5c06662

We report planar tunneling spectroscopy measurements on metal- WSe2-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 moire 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.

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