Orateur
Description
Eight years after the discovery of superconductivity in magic-angle twisted bilayer graphene, its pairing symmetry is not definitively established. I will first discuss existing experimental and theoretical constraints on the SC order parameter. I will then focus on Andreev spectroscopy, which is a phase sensitive probe uniquely suited to address this issue. I will describe recent theoretical work [1] which highlights problems in the analysis of existing Andreev experiments and provides a natural explanation of puzzling features in the data that can only be understood in terms of Andreev bound states in a superconductor with an unconventional, sign-changing order parameter. I will end with predictions [2] for Andreev experiments in an in-plane magnetic field that would determine the spin wavefunction of the Cooper pairs and unambiguously distinguish between the allowed pairing symmetries.
[1] S. Biswas, S. Suman, M. Randeria, R. Sensarma, PNAS 122, e2509881122 (2025)
[2] S. Biswas, R. Sensarma, M. Randeria, arXiv:2606.xxxx (to appear)