Superconductivity and multiple pressure-induced phases in BaPt$_2$As$_2$

TL;DR

BaPt$_2$As$_2$ exhibits charge density wave order and multiple pressure-induced phases, with superconductivity emerging and evolving under pressure, making it a promising system for studying competing electronic interactions.

Contribution

This study reveals the complex phase diagram of BaPt$_2$As$_2$, including charge density wave order and pressure-induced phase transitions, linking high-temperature instabilities to superconductivity.

Findings

Charge density wave order at room temperature and ambient pressure.

Multiple pressure-induced phase transitions at high temperatures.

Superconducting transition temperature $T_c$ varies with pressure.

Abstract

The newly discovered BaPt$_2$As$_2$ shows a structural distortion at around 275~K, followed by the emergence of superconductivity at lower temperatures. Here we identify the presence of charge density wave (CDW) order at room temperature and ambient pressure using single crystal x-ray diffraction, with both a superlattice and an incommensurate modulation, where there is a change of the superlattice structure below $\simeq$ 275~K. Upon applying pressure, BaPt$_2$As$_2$ shows a rich temperature-pressure phase diagram with multiple pressure-induced transitions at high temperatures, the emergence or disappearance of which are correlated with sudden changes in the superconducting transition temperature $T_c$. These findings demonstrate that BaPt$_2$As$_2$ is a promising new system for studying competing interactions and the relationship between high-temperature electronic instabilities and superconductivity.