Superconductivity distorted by the coexisting pseudogap in the antinodal region of Bi$_{1.5}$Pb$_{0.55}$Sr$_{1.6}$La$_{0.4}$CuO$_{6+\delta}$: A photon-energy-dependent angle-resolved photoemission study

TL;DR

This study uses photon-energy-dependent ARPES to reveal how the pseudogap distorts the superconducting gap in cuprates, showing the coexistence of two features and challenging simple gap models.

Contribution

It demonstrates the importance of background correction in ARPES and provides new insights into the interplay between pseudogap and superconductivity in cuprates.

Findings

Antinodal spectra show two coexisting features attributed to pseudogap and superconductivity.

Background signals at low photon energies can mislead gap size evaluation.

Spectral gap deviates from a simple d-wave form due to pseudogap competition.

Abstract

The interplay between superconductivity and the pseudogap is an important aspect of cuprate physics. However, the nature of the pseudogap remains controversial, in part because different experiments have suggested different gap functions. Here we present a photon-energy-dependence angle-resolved photoemission spectroscopy (ARPES) study on Bi$_{1.5}$Pb$_{0.55}$Sr$_{1.6}$La$_{0.4}$CuO$_{6+\delta}$. We find that antinodal ARPES spectra at low photon energies are dominated by background signals which can lead to a misevaluation of the spectral gap size. Once background is properly accounted for, independent of photon energy, the antinodal spectra robustly show two coexisting features at different energies dominantly attributed to the pseudogap and superconductivity, as well as an overall spectral gap which deviates from a simple d-wave form. These results support the idea that the spectral gap is distorted due to the competition between the pseudogap and superconductivity.