Bulk superconductivity at 84 K in the strongly overdoped regime of cuprates

TL;DR

This study reveals bulk superconductivity at 84 K in heavily overdoped cuprates, challenging the conventional understanding that high $T_c$ requires a non-Fermi liquid ground state, by showing Fermi liquid-like behavior in an unusual phase.

Contribution

It demonstrates the existence of a high-$T_c$ superconducting phase in heavily overdoped cuprates with Fermi liquid characteristics, contrary to prior assumptions.

Findings

Bulk superconductivity at 84 K in overdoped regime

Superfluid density similar to optimally doped cuprates

Large electronic specific heat indicating unpaired holes

Abstract

By means of magnetization, specific heat and muon-spin relaxation measurements, we investigate high-pressure oxidized \mohpo, in which overdoping is achieved up to $p \sim 0.45$ hole/Cu, well beyond the $T_c - p$ superconducting dome of cuprates, where Fermi liquid behavior is expected. Surprisingly, we find bulk superconductivity with $T_c$=84 K and superfluid density similar to those of optimally doped Y123. On the other hand, specific heat data display a large electronic contribution at low temperature, comparable to that of nonsuperconducting overdoped La214. These results point at an unusual high-$T_c$ phase with a large fraction of unpaired holes. Further experiments may assess the Fermi liquid properties of the present phase, which would put into question the paradigm that the high $T_c$ of cuprates originates from a non-Fermi liquid ground state.