Monotonic d-wave Superconducting Gap in Optimally-Doped Bi$_2$Sr$_{1.6}$La$_{0.4}$CuO$_6$ Superconductor by Laser-Based Angle-Resolved Photoemission Spectroscopy

TL;DR

This study uses laser-based ARPES to reveal that the pseudogap in optimally-doped Bi2201 has a similar momentum dependence as the superconducting gap, suggesting a close relationship and possible precursor role.

Contribution

It provides high-resolution evidence that the pseudogap and superconducting gap share similar properties, supporting the precursor hypothesis in cuprate superconductors.

Findings

Superconducting gap exhibits a standard d-wave form.

Pseudogap opens above T_c over a large Fermi surface region.

Pseudogap and superconducting gap show similar momentum dependence.

Abstract

The momentum and temperature dependence of the superconducting gap and pseudogap in optimally-doped Bi$_2$Sr$_{1.6}$La$_{0.4}$CuO$_6$ superconductor is investigated by super-high resolution laser-based angle-resolved photoemission spectroscopy. The measured energy gap in the superconducting state exhibits a standard {\it d}-wave form. Pseudogap opens above T$_c$ over a large portion of the Fermi surface with a "Fermi arc" formed near the nodal region. In the region outside of the "Fermi arc", the pseudogap has the similar magnitude and momentum dependence as the gap in the superconducting state which changes little with temperature and shows no abrupt change across T$_c$. These observations indicate that the pseudogap and superconducting gap are closely related and favor the picture that the pseudogap is a precursor to the superconducting gap.