High-Tc superconductors under very high pressure

High pressure has played a crucial role in the short history of high Tc superconductors. Soon after the discovery of superconductivity by Bednorz and Muller in La-Ba-Cu-O, Chu et al. showed that the critical temperature Tc could be significantly increased by pressure. This observation led to the discovery of YBa2Cu3O7 by Wu et al. with a Tc above 90 K. Incidentally, this high Tc is probably also due to the fact that YBa2Cu3O7 has two CuO2layers per unit cell instead of a single one in La-Ba-Cu-O. The authors discuss the high pressure dependence of the oxide superconductors, particularly at pressures above 10 GPa, and the nonmonotonic dependence of transition temperature on pressure