Crossover from two-dimensional to three-dimensional superconducting states in bismuth-based cuprate superconductor

TL;DR

This study reveals a pressure-induced transition from two-dimensional to three-dimensional superconducting states in a cuprate superconductor, providing insights into the nature of the strange metal phase and high-temperature superconductivity.

Contribution

First experimental observation of a pressure-driven crossover from 2D to 3D superconductivity in a cuprate, elucidating the dimensional nature of the strange metal phase.

Findings

Pressure above 2.8 GPa induces 2D to 3D superconducting crossover.

2D superconducting transition shows Berezinski-Kosterlitz-Thouless-like behavior.

Strange metal phase is predominantly two-dimensional.

Abstract

To decipher the mechanism of high temperature superconductivity, it is important to know how the superconducting pairing emerges from the unusual normal states of cuprate superconductors, including pseudogap, anomalous Fermi liquid and strange metal (SM). A long-standing issue under debate is how the superconducting pairing is formed and condensed in the SM phase because the superconducting transition temperature is the highest in this phase. Here, we report the first experimental observation of a pressure-induced crossover from two- to three-dimensional superconducting states in the optimally-doped Bi2Sr2CaCu2O8+delta bulk superconductor at a pressure above 2.8 GPa, through state-of-the-art in-situ high-pressure measurements of resistance, magnetoresistance and magnetic susceptibility. By analyzing the temperature dependence of resistance, we find that the two-dimensional (2D) superconducting transition exhibits a Berezinski-Kosterlitz-Thouless-like behavior. The emergence of this 2D superconducting transition provides direct and strong evidence that the SM state is predominantly 2D-like. This is important to a thorough understanding of the phase diagram of cuprate superconductors.