We present a theory for the ground state of multi-component p-wave and d-wave unconventional superconductors on the hexagonal lattice. We show that the electromagnetic field fluctuations play a crucial role in selecting between the nematic and chiral solutions below Tc. Specifically, we derive an effective free energy for the two-component superconducting order parameter after integrating out the electromagnetic field fluctuations just above the superconducting transition. The effects of such fluctuations are encoded in a non-analytic term which is cubic in the order parameter and which generally favors a nematic superconducting state being realized below Tc. We discuss how our result may be applied to twisted bilayer graphene.

Virginia Gali

University of Minnesota