Observation of superconductivity and its enhancement at the charge density wave critical point in LaAgSb$_2$

TL;DR

This study reports the discovery of superconductivity in LaAgSb$_2$, which is enhanced near the charge density wave critical point under pressure, highlighting the interplay between CDW and superconductivity.

Contribution

It reveals the emergence and enhancement of superconductivity at the CDW critical point in LaAgSb$_2$, and suggests additional mechanisms beyond electron-phonon coupling.

Findings

Superconductivity appears at ambient pressure in LaAgSb$_2$.

The superconducting transition temperature peaks sharply at 3.2 GPa.

Additional mechanisms reinforce superconductivity near the CDW critical pressure.

Abstract

We discover superconductivity (SC) in LaAgSb$_2$ at ambient pressure and its close correlation with a charge density wave (CDW) under pressure. The superconducting transition temperature ($T_c$) exhibits a sharp peak at the CDW critical pressure of 3.2 GPa. We demonstrate that the carriers inhabiting the Sb-square net is crucial not only in the formation of CDW but also in SC for their relatively strong electron-phonon coupling (EPC). Furthermore, theoretical EPC strength in pristine LaAgSb$_2$ cannot explain the observed peak with $T_c\sim 1$ K, which indicates that an additional mechanism reinforces SC only around the CDW critical pressure.