Common superconducting transition in under and overdoped cuprate superconductors

TL;DR

This paper demonstrates that both underdoped and overdoped cuprate superconductors share a common superconducting transition mechanism, challenging the traditional view that overdoped cuprates become Fermi liquids with diminished superconductivity.

Contribution

The study reproduces experimental results showing superconducting gaps beyond the critical doping and models the system as a mesoscopic granular superconductor with Josephson junctions.

Findings

Superconducting long-range order exists in both underdoped and overdoped cuprates.

Charge inhomogeneity leads to localized superconducting amplitudes.

Critical temperature is determined by Josephson coupling in a granular superconductor model.

Abstract

Underdoped cuprate superconductors are believed to be strongly correlated with electronic systems with small phase stiffness leading to a large phase fluctuation region is known as the pseudogap state. With increasing doping it is generally agree that they become Fermi liquid, rendering the end of the superconductivity due to the sufficiently large electronic screening. However, this scenario does not stand against a recent experiment\cite{OverJJ2022} that combined magnetic susceptibility and Scanning Tunnelling Microscopy (STM) which measured superconducting gaps and amplitudes amid charge inhomogeneity far beyond the critical doping $p_{\rm c} \approx 0.27$. We reproduced these results by calculating the localized superconducting amplitudes that emerge out of charge inhomogeneities, which forms a mesoscopic granular superconductor with an array of Josephson junctions, whose average couplings determine the critical temperature $T_{\rm c}$. The calculations agree with the experiments and both yield that underdoped and overdoped compounds have superconducting long-range order by the same mechanism.