High-pressure phase relations of Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ single crystals

TL;DR

This study explores how the superconducting transition temperature of Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ single crystals varies under high pressure up to 18 GPa, revealing a saturation and subsequent decrease in $T_{c}$, influenced by doping levels.

Contribution

It provides the first detailed high-pressure phase diagram of Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ and interprets the results through a model involving competition between carrier density and pairing strength.

Findings

$T_{c}$ increases then saturates at a critical pressure $P_{c}$

Oxygen doping reduces the increase in $T_{c}$ and $P_{c}$

A new high-pressure phase diagram is established

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.