Electronic structure of the ingredient planes of cuprate superconductor Bi2Sr2CuO6+{\delta}: a comparison study with Bi2Sr2CaCu2O8+{\delta}

TL;DR

This study uses low-temperature STM to compare the electronic structures of BiO and SrO planes in two cuprate superconductors, revealing how interstitial oxygen dopants influence pseudogap and van Hove singularity features, and providing insights into their differing superconducting properties.

Contribution

It provides a comparative analysis of the electronic structures of Bi-2201 and Bi-2212, highlighting the role of interstitial oxygen dopants and structural differences in their electronic behavior and superconductivity.

Findings

VHS occurs only on SrO in Bi-2212, but on both BiO and SrO in Bi-2201.

Interstitial oxygen dopants are primary causes for VHS occurrence.

Pseudogap is unrelated to superconductivity in these materials.

Abstract

By means of low-temperature scanning tunneling microscopy, we report on the electronic structures of BiO and SrO planes of Bi2Sr2CuO6+{\delta} (Bi-2201) superconductor prepared by argon-ion bombardment and annealing. Depending on post annealing conditions, the BiO planes exhibit either pseudogap (PG) with sharp coherence peaks and an anomalously large gap of 49 meV or van Hove singularity (VHS) near the Fermi level, while the SrO is always characteristic of a PG-like feature. This contrasts with Bi2Sr2CaCu2O8+{\delta} (Bi-2212) superconductor where VHS occurs solely on the SrO plane. We disclose the interstitial oxygen dopants ({\delta} in the formulas) as a primary cause for the occurrence of VHS, which are located dominantly around the BiO and SrO planes, respectively, in Bi-2201 and Bi-2212. This is supported by the contrasting structural buckling amplitude of BiO and SrO planes in the two superconductors. Our findings provide solid evidence for the irrelevance of PG to the superconductivity in the two superconductors, as well as insights into why Bi-2212 can achieve a higher superconducting transition temperature than Bi-2201, and by implication, the mechanism of cuprate superconductivity.