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

摘要

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