Mapping the Electronic Structure of Each Ingredient Oxide Layer of High-$T_ extrm{c}$ Cuprate Superconductor Bi2Sr2CaCu2O8+{\delta}

摘要

Understanding the mechanism of high transition temperature (Tc)superconductivity in cuprates has been hindered by the apparent complexity oftheir multilayered crystal structure. Using a cryogenic scanning tunnelingmicroscopy, we report on layer-by-layer probing of the electronic structures ofall ingredient planes (BiO, SrO, CuO2) of Bi2Sr2CaCu2O8+{\delta} superconductorprepared by argon-ion bombardment and annealing technique. We show that thewell-known pseudogap (PG) feature observed by STM is inherently a property ofthe BiO planes and thus irrelevant directly to Cooper pairing. The SrO planesexhibit an unexpected Van Hove singularity near the Fermi level, while the CuO2planes are exclusively characterized by a smaller gap inside the PG. The smallgap becomes invisible near Tc, which we identify as the superconducting gap.The above results constitute severe constraints on any microscopic model forhigh Tc superconductivity in cuprates.