Restoring superconductivity in hole dope Pr2CuO4 via high pressure phase transitions

The hole-doped lanthanum cuprates, based on Ruddlesden-Popper n = 1 (RP1) La2CuO4, have attracted intense focus since the discovery of superconductivity in La2-xBaxCuO4 (LBCO). Maximum superconducting Tc of 38 K was quickly established in La2-xSrxCuO4 in the early 90s. While it has been understood for a while that the maximum in Tc occurs at A = La2-xSrx as it has the minimum variance in A-site ionic radii, we have very recently managed to provide the underlying structural basis for this. Our detailed single crystal diffraction studies showing that suppression of Tc in compositions with larger variances are linked to intrinsic electronic separation (EPS) between low-temperature orthorhombic phase (superconducting) and low-temperature tetragonal (charge density wave ordered) phases. Motivated by a desire to suppress EPS and hence prepare new pristine system for studying high-Tc superconductivity in, we have recently prepared phase pure samples of Pr2-xCaxCuO4, whose A-site variance is zero within the precision of the reported Shannon ionic radii. While this compound crystalise in the Nd2CuO4 type structure, there are indications in the literature that the parent undoped compounds undergo an irreversible phase transition to the RP1 type phase at high pressures. Here we propose a high pressure in situ diffraction study on PEARL to investigate the reversable and irreversible phase transitions in this system.