Measurement of an Anisotropic Energy Gap in Single Plane Bi_2Sr_(2-x)La_xCuO_(6+d)

TL;DR

This study uses angle-resolved photoemission spectroscopy to investigate the anisotropic energy gap in single-layer Bi-based cuprate superconductors, revealing persistent normal-state gaps and their possible link to pairing interactions.

Contribution

It provides the first detailed measurement of the anisotropic energy gap in single-plane Bi_2Sr_{2-x}La_xCuO_{6+d}, highlighting similarities between normal and superconducting states.

Findings

The energy gap is highly anisotropic with a maximum smaller than in bilayer cuprates.

The gap persists above T_c, similar to underdoped bilayer cuprates.

Normal-state and superconducting gaps have similar magnitude and anisotropy, suggesting a common origin.

Abstract

We report angle-resolved photoemission spectra both above and below T_c in the single-plane cuprate superconductor Bi_2Sr_{2-x}La_xCuO_{6+d}. The superconducting state measurements show a highly anisotropic excitation gap with a maximum magnitude smaller than that of the bilayer compound Bi_2Sr_2CaCu_2O_8 by a factor of 3. For a range of doping, the gap persists well above T_c, behavior previously associated with underdoped bilayer cuprates. The anisotropy and magnitude of the normal-state gap are very similar to the superconducting state gap, indicating that the two gaps may have a common origin in a pairing interaction.