Pressure-induced anomalous enhancement in superconducting critical temperature of transition-metal chalcogenide Ta$_2$PdS$_6$ and Ta$_2$PdSe$_6$

TL;DR

This study reveals pressure-induced enhancement of superconducting critical temperature in Ta$_2$PdS$_6$ and Ta$_2$PdSe$_6$ at pressures above 100 GPa, uncovering a second superconducting dome with record T$_c$ values in these materials.

Contribution

First high-pressure measurements above 100 GPa on Ta$_2$PdS$_6$ and Ta$_2$PdSe$_6$, demonstrating the emergence of a second superconducting dome and record T$_c$ values.

Findings

Superconducting T$_c$ increases drastically above 100 GPa.

Maximum T$_c$ of 11.2 K in Ta$_2$PdS$_6$ at 130 GPa.

Emergence of a second superconducting dome at ultra-high pressures.

Abstract

The emergence of a second dome in the superconducting phase through pressure-driven manipulation of crystal structures in materials has attracted considerable attention. Transition metal chalcogenides (TMCs) represent a highly promising platform, as the second dome has been observed in several binary compounds. Recently, ternary TMCs such as Ta$_2$PdS$_6$ and Ta$_2$PdSe$_6$ have exhibited pressure-induced superconducting domes. In this study, we perform electrical transport measurements of Ta$_2$PdS$_6$ and Ta$_2$PdSe$_6$ under extremely high pressures exceeding 100 GPa, namely uninvestigated regions in previous reports, to reveal the emergence of the second dome. The superconducting critical temperatures (T$_c$) in both Ta$_2$PdS$_6$ and Ta$_2$PdSe$_6$ initially decrease with increasing pressure. Subsequently, the Tcs tend to enhance drastically above 100 GPa. Notably, the maximum T$_c$ in Ta$_2$PdS$_6$ is 11.2 K at 130.0 GPa, which is a relatively high record among the TMCs. The emergence of the second dome in Ta$_2$PdS$_6$ and Ta$_2$PdSe$_6$ opens further motivation for the investigation under extreme conditions beyond the first dome to find hidden ordered phases.