Gap anisotropy in nematic quantum critical superconductors

When pairing is driven by nematic quantum fluctuations, it results in a unique form of superconductivity. Nematic fluctuations, while anisotropic, couple to the entire Fermi surface, in contrast to, e.g. spin fluctuations that typically couple to so-called ‘hotspots’. The result is an entire series of possible anisotropic pairing states, with closely spaced condensation temperatures, all with s-wave symmetry. The existence of these states drives a strong temperature evolution of the anisotropy of the superconducting gap. This evolution is a direct consequence of critical fluctuations, and provides a clear signature of quantum criticality inside the superconducting state.