Pure nematic quantum critical point accompanied by a superconducting dome

TL;DR

This study provides evidence that a pure electronic nematic quantum critical point in FeSe$_{1-x}$Te$_{x}$ is associated with a superconducting dome, highlighting the role of nematic fluctuations in unconventional superconductivity.

Contribution

It demonstrates the existence of a nematic quantum critical point in FeSe$_{1-x}$Te$_{x}$ and links it to a superconducting dome, a novel finding in nematic quantum criticality research.

Findings

Nematic QCP shows diverging nematic susceptibility.

Superconducting dome centered at the nematic QCP in FeSe$_{1-x}$Te$_{x}$.

Contrast with FeSe$_{1-x}$S$_{x}$ where no QCP-related superconductivity enhancement.

Abstract

When a symmetry-breaking phase of matter is suppressed to a quantum critical point (QCP) at absolute zero, quantum-mechanical fluctuations proliferate. Such fluctuations can lead to unconventional superconductivity, as evidenced by the superconducting domes often found near magnetic QCPs in correlated materials. However, it remains unclear whether this superconductivity mechanism holds for QCPs of the electronic nematic phase, characterized by rotational symmetry breaking. Here, we demonstrate from systematic elastoresistivity measurements that nonmagnetic FeSe$_{1-x}$Te$_{x}$ exhibits an electronic nematic QCP showing diverging nematic susceptibility. This finding establishes two nematic QCPs in FeSe-based superconductors with contrasting accompanying phase diagrams. In FeSe$_{1-x}$Te$_{x}$, a superconducting dome is centered at the QCP, whereas FeSe$_{1-x}$S$_{x}$ shows no QCP-associated enhancement of superconductivity. We find that this difference is related to the relative strength of nematic and spin fluctuations. Our results in FeSe$_{1-x}$Te$_{x}$ present the first case in support of the superconducting dome being associated with the pure nematic QCP.