High-pressure phase relations of Bi${}_2$Sr${}_2$CaCu${}_2$O${}_{8+\delta }$ single crystals

Abstract

We have investigated the pressure dependence of the superconducting transition temperature $T_c$ up to 18 GPa of Bi${}_2$Sr${}_2$CaCu${}_2$O${}_{8+\delta }$ single crystals ranging from the highly underdoped through the nearly optimally doped to the highly overdoped level. For all three samples studied, $T_c$ is found to increase initially and then saturate at a critical pressure $P_c$ but decrease modestly with further compression. Oxygen doping tends to reduce the increase in $T_c$ and $P_c$. A new high-pressure phase diagram between the saturated $T_c$ and $P_c$ is then obtained. Theoretical interpretation is given by using the competition between the hole carrier density and pairing interaction strength based on the high-pressure transport data of the resistivity and Hall coefficient in this system.

8 pages, 7 figures, to appear in Physical Review B