Possible Mechanisms to Stabilize Nematic Superconductivity

The discovery of two superconducting transitions in UPt₃ opened many new questions. The most pressing of which was the stablitiy of the A nematic state when weak-coupling theories predicted that the time-reversal symmetry breaking state is stable across the whole phase diagram. In this talk, we present a mechanism where a generalized spin fluctuation feedback effect can stabilize the nematic state by coupling superconductivity to electronic fluctuations [1]. This effect provides a unifying explanation for the existence of nematic states in the heavy fermions which show two transitions while additonally constraining the possible order parameters. We shall also connect this to reports of nematic superconductivity in twisted bilayer graphene.

[1] A. Amin and D.F. Agterberg , "Generalized spin fluctuation feedback in heavy fermion superconductors", Phys. Rev. Research 2, 013381 (2020)