Nematic superconductivity stabilized by density wave fluctuations: Possible application to twisted bilayer graphene

TL;DR

This paper proposes a mechanism where strong density wave fluctuations in two dimensions stabilize nematic superconductivity, providing insight into rotational symmetry breaking observed in twisted bilayer graphene.

Contribution

It introduces a new theoretical framework showing how density wave fluctuations can favor nematic superconductivity over chiral states.

Findings

Density wave fluctuations enhance nematic superconductivity

Weak-coupling theory favors chiral states

Explains rotational symmetry breaking in twisted bilayer graphene

Abstract

Nematic superconductors possess unconventional superconducting order parameters that spontaneously break rotational symmetry of the underlying crystal. In this work we propose a mechanism for nematic superconductivity stabilized by strong density wave fluctuations in two dimensions. While the weak-coupling theory finds the fully gapped chiral state to be energetically stable, we show that strong density wave fluctuations result in an additional contribution to the free energy of a superconductor with multicomponent order parameters, which generally favors nematic superconductivity. Our theory shades light on the recent observation of rotational symmetry breaking in the superconducting state of twisted bilayer graphene.