Nematicity-enhanced superconductivity in systems with a non-Fermi liquid behavior

TL;DR

This paper investigates how nematicity enhances superconductivity in flat-band systems with non-Fermi liquid behavior, revealing a new pairing symmetry and increased transition temperatures driven by many-body effects.

Contribution

It demonstrates that nematicity, driven by many-body effects in flat-band systems, systematically boosts superconducting transition temperatures and alters pairing symmetry.

Findings

Nematicity enhances $T_c$ in flat-band systems.

A new $s_{x^2+y^2} - d_{x^2-y^2} - d_{xy}$ pairing symmetry emerges.

Electrons exhibit non-Fermi liquid behavior in the studied models.

Abstract

We explore the interplay between nematicity~(spontaneous breaking of the sixfold rotational symmetry), superconductivity, and non-Fermi liquid behavior in partially flat-band models on the triangular lattice. A key result is that the nematicity (Pomeranchuk instability), which is driven by many-body effect and stronger in flat-band systems, enhances superconducting transition temperature in a systematic manner on the $T_{\rm c}$ dome. There, a $s_{x^2+y^2} - d_{x^2-y^2} - d_{xy}$-wave symmetry, in place of the conventional $d_{x^2-y^2}$-wave, governs the nematicity-enhanced pairing with a sharp rise in the $T_{\rm c}$ dome on the filling axis. When the sixfold symmetry is spontaneously broken, the pairing becomes more compact in real space than in the case when the symmetry is enforced. These are accompanied by a non-Fermi character of electrons in the partially flat bands with many-body interactions.