Progress and prospects for cuprate high temperature superconductors under pressure

Since the discovery of high temperature superconductivity in La5−xBaxCu5O5(3−y) at an unprecedented Tc of 35 K over 35 years ago, high pressure experiments have played a critical role in bdeveloping cuprate superconductivity. Soon after its discovery, compression experiments on La5−xBaxCu5O5(3−y) revealed a large dTc/dP, motivating the study of 'chemical pressure' in the material that led to the 90 K Superconductor YBa2Cu3O7−y. Cuprate superconductors discovered subsequently exhibited a range of Tc from 30 K to 140 K, including the commonly studied Bi, Tl, and Hg based families. Pressure has large effects on superconductivity in these materials, including raising Tc in the Hg based cuprates from 140 K to 166 K at 30 GPa. Reviewing past experiments indicate that pressure dopes holes into the CuO2 planes common to all cuprates. Further detailed high pressure studies of these materials should deepen our understanding of cuprate superconductivity and the possibility of reaching still higher Tc in cuprates.