Evolution from a nodeless gap to d(x2-y2) form in underdoped La(2-x)SrxCuO4

TL;DR

This study uses ARPES to track how the electronic gap in underdoped La(2-x)SrxCuO4 evolves from a nodeless form to a d(x2-y2) symmetry with increasing temperature or doping, shedding light on the pairing mechanism in cuprates.

Contribution

It provides detailed ARPES evidence of the gap evolution in underdoped cuprates, crucial for understanding the order parameter symmetry and superconductivity emergence.

Findings

Gapped spectra along the entire Fermi surface at low temperatures.

Evolution of the gap to a d(x2-y2) form with doping and temperature.

Insights into the symmetry of the order parameter in underdoped cuprates.

Abstract

Using angle-resolved photoemission (ARPES), it is revealed that the low-energy electronic excitation spectra of highly underdoped superconducting and non-superconducting La(2-x)SrxCuO4 cuprates are gapped along the entire underlying Fermi surface at low temperatures. We show how the gap function evolves to a d(x2-y2) form as increasing temperature or doping, consistent with the vast majority of ARPES studies of cuprates. Our results provide essential information for uncovering the symmetry of the order parameter(s) in strongly underdoped cuprates, which is a prerequisite for understanding the pairing mechanism and how superconductivity emerges from a Mott insulator.