Evolution of the gaps through the cuprate phase-diagram

TL;DR

This study uses electronic Raman scattering to investigate the evolution of the antinodal gap in mercury-based cuprates across different doping levels, revealing a transition from a superconducting gap to a disconnected state near optimal doping.

Contribution

It provides new insights into the doping-dependent nature of the antinodal gap and its relationship with superconductivity in cuprates, identifying a critical doping point.

Findings

Antinodal gap is a true superconducting gap in overdoped cuprates.

A breakpoint near optimal doping separates different gap behaviors.

The normal and superconducting states differ significantly across the doping range.

Abstract

The actual physical origin of the gap at the antinodes, and a clear identification of the superconducting gap are fundamental open issues in the physics of high-$T_c$ superconductors. Here, we present a systematic electronic Raman scattering study of a mercury-based single layer cuprate, as a function of both doping level and temperature. On the deeply overdoped side, we show that the antinodal gap is a true superconducting gap. In contrast, on the underdoped side, our results reveal the existence of a break point close to optimal doping below which the antinodal gap is gradually disconnected from superconductivity. The nature of both the superconducting and normal state is distinctly different on each side of this breakpoint.