Superconductivity and multiple pressure-induced phases in BaPt2As2

The recently discovered BaPt2As2 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 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 ≃275 K. Upon applying pressure, BaPt2As2 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 Tc. These findings demonstrate that BaPt2As2 is a promising system for studying competing interactions and the relationship between high-temperature electronic instabilities and superconductivity.