Symmetry constraints on superconductivity in twisted bilayer graphene: Fractional vortices, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>4</mml:mn><mml:mi>e</mml:mi></mml:mrow></mml:math> condensates, or nonunitary pairing

Abstract

Twisted bilayer graphene has recently emerged as an exciting platform to study interaction-driven phases. Among these, superconductivity has received intense theoretical effort to understand its underlying mechanism. In this work, the authors establish general symmetry constraints on the nature of superconductivity in twisted bilayer graphene that are independent of its mechanism. These constraints are sufficient to limit the nature of superconductivity to one of three unconventional possibilities: nonunitary pairing, unitary pairing with fractional vortices, or higher-charge condensates. They identify parameter regimes where each possibility is likely to occur.

Topics & Concepts