Additional electron pairing in a d-wave superconductor driven by nematic order

TL;DR

This paper predicts that nematic fluctuations in d-wave superconductors can induce a full energy gap and an additional s-wave pairing, leading to a new superconducting phase near the quantum critical point.

Contribution

It provides a non-perturbative analysis showing how nematic order can generate a dynamical nodal gap and induce a fully gapped superconducting state in d-wave superconductors.

Findings

Nematic fluctuations can open a dynamical nodal gap.

A fully gapped d+is superconducting phase emerges near the quantum critical point.

Fermion velocity renormalization saturates due to the gap formation.

Abstract

We perform a non-perturbative analysis of the strong interaction between gapless nodal fermions and the nematic order parameter in two-dimensional d_{x^2-y^2} superconductors. We predict that the critical nematic fluctuation can generate a dynamical nodal gap if the fermion flavor N is smaller than a threshold N_c. Such gap generation leads to an additional is-wave Cooper pairing instability, which induces a fully gapped d_{x^2-y^2}+is superconducting dome in the vicinity of the nematic quantum critical point. The opening of a dynamical gap has important consequences, including the saturation of fermion velocity renormalization, a weak confinement of fermions and the suppression of observable quantities.