Superconductivity near a nematoelastic quantum critical point

TL;DR

This paper investigates how nematoelastic coupling affects superconductivity near a nematic quantum critical point, revealing a suppression of critical temperature and gap, and providing insights into phase transitions and experimental observations in FeSe compounds.

Contribution

It demonstrates that nematoelastic coupling reduces superconducting critical temperature and gap, and explores phase transition behaviors near a nematic quantum critical point.

Findings

Nematoelastic coupling decreases T_c and Δ regardless of gap symmetry.

Phase transitions exhibit different critical exponents depending on the normal state.

Results may explain T_c behavior in FeSe$_{1-x}$S$_x$ near nematic quantum criticality.

Abstract

We study the pairing instability of a two-dimensional metallic system induced by Ising-nematic quantum fluctuations in the presence of an unavoidable relevant coupling of the nematic order parameter to the elastic modes (acoustic phonons) of the lattice. We find that this nematoelastic coupling $\lambda_\mathrm{latt}$ leads to a decrease of both the superconducting (SC) critical temperature $T_c$ and the gap function $\Delta$, regardless of the gap symmetry. Interestingly, we show that $\lambda_\mathrm{latt}$ provides a knob that allows us to investigate the emergence of the SC phase at low temperatures, as an instability from either a non-Fermi liquid or a Fermi liquid normal state. The phase transitions between the SC and these normal states are characterized by different critical exponents, which may also vary for each gap symmetry. Finally, we argue that these results might explain the dependence of $T_c$ in the vicinity of the nematic quantum critical point exhibited by the compound FeSe$_{1 - x}$S$_x$.