The coherent {\it d}-wave superconducting gap in underdoped La$_{2-x}$Sr$_{x}$CuO$_4$ as studied by angle-resolved photoemission

TL;DR

This study uses ARPES to reveal a coherent d-wave superconducting gap in underdoped La$_{2-x}$Sr$_{x}$CuO$_4$, showing sharp spectral peaks and a simple gap structure consistent across different doping levels.

Contribution

First ARPES study to observe sharp spectral peaks along the entire Fermi surface in underdoped La$_{2-x}$Sr$_{x}$CuO$_4$, confirming a single d-wave gap in these materials.

Findings

Sharp spectral peaks observed in underdoped samples

Superconducting gap follows a simple d-wave form

Maximum gap of 14 meV and 26 meV in different doping levels

Abstract

We present angle-resolved photoemission spectroscopy (ARPES) data on moderately underdoped La$_{1.855}$Sr$_{0.145}$CuO$_4$ at temperatures below and above the superconducting transition temperature. Unlike previous studies of this material, we observe sharp spectral peaks along the entire underlying Fermi surface in the superconducting state. These peaks trace out an energy gap that follows a simple {\it d}-wave form, with a maximum superconducting gap of 14 meV. Our results are consistent with a single gap picture for the cuprates. Furthermore our data on the even more underdoped sample La$_{1.895}$Sr$_{0.105}$CuO$_4$ also show sharp spectral peaks, even at the antinode, with a maximum superconducting gap of 26 meV.