On the Relationship Between the Pseudo- and Superconducting Gaps: Effects of Residual Pairing Correlations Below Tc

TL;DR

This paper investigates the residual pseudogap below Tc in underdoped cuprates, revealing its impact on the superconducting excitation gap and order parameter through a diagrammatic BCS-BEC crossover theory.

Contribution

It introduces a conserving diagrammatic BCS-BEC crossover framework to analyze the evolution of the pseudogap into the superconducting state, highlighting distinctions between the gap and order parameter.

Findings

Residual pseudogap persists below Tc affecting superconducting properties.

The theory reproduces weak coupling BCS results and Leggett's zero-temperature limit.

Implications for interpreting spectroscopic data in underdoped cuprates.

Abstract

The existence of a normal state spectral gap in underdoped cuprates raises important questions about the associated superconducting phase. For example, how does this pseudogap evolve into its below Tc counterpart? In this paper we characterize this unusual superconductor by investigating the nature of the ``residual'' pseudogap below Tc and, find that it leads to an important distinction between the superconducting excitation gap and order parameter. Our approach is based on a conserving diagrammatic BCS Bose-Einstein crossover theory which yields the precise BCS result in weak coupling at any T<Tc and reproduces Leggett's results in the T=0 limit. We explore the resulting experimental implications.