Prominent Cooper Pairing Away From the Fermi Level and its Spectroscopic Signature in Twisted Bilayer Graphene

TL;DR

This paper demonstrates that phonon-mediated Cooper pairing away from the Fermi level significantly enhances superconductivity in twisted bilayer graphene, producing unique spectroscopic signatures and asymmetric phase diagrams.

Contribution

It introduces a full-bandwidth multiband Eliashberg approach to analyze pairing away from the Fermi level in twisted bilayer graphene, revealing new mechanisms for superconductivity.

Findings

Pairing away from the Fermi level boosts critical temperature.

Superconducting domes exhibit particle-hole asymmetry.

Distinct spectroscopic features are predicted for experiments.

Abstract

We investigate phonon-mediated Cooper pairing in flat electronic band systems by solving the full-bandwidth multiband Eliashberg equations for superconductivity in magic angle twisted bilayer graphene using a realistic tight-binding model. We find that Cooper pairing away from the Fermi level contributes decisively to superconductivity by enhancing the critical temperature and ensures a robust finite superfluid density. We show that this pairing yields particle-hole asymmetric superconducting domes in the temperature-gating phase diagram and gives rise to distinct spectroscopic signatures in the superconducting state. We predict several such features in tunneling and angle resolved photoemission spectra for future experiments.