Effects of pressure on high Tc superconductors

Pressure is an important research tool in understanding the nature of superconductivity and in the development of new superconducting materials. Experiments have been performed at NRL at pressures to 7 GPa on single crystals of Tl2Ba2CaCu2O8+δ, Tl2Ba2Ca2Cu3O10−γ, and NdBa2Cu3O7−δ. All three materials exhibit a positive dTc/dP which decreases with increasing pressure; in several instances, an extremium in Tc(P) is found. For Tl2Ba2Ca2Cu3O10−x, Tc was observed to increase from 116 K at atmospheric pressure, to a value as high as 131.8±0.5 K at 7 GPa. Measurements of Tc(P) on NdBa2Cu3O7−δ were found to be in conflict with an empirical prediction for this material.