Atomically Resolved STM/STS Observation on the Edge of CuO2 and (BiO)2 Layers of Bi-Sr-Ca-Cu-O

Abstract

Atomic resolution STM observation of the layered structure of an oxide superconductor has been achieved for the first time. The relative contributions to the electronic states from the CuO₂ and (BiO)₂ layers were remarkably different depending on the tunneling bias voltage, reflecting the two-dimensional nature of the electronic structure of Bi₂Sr₂CaCu₂O _y . STS on each layer indicated the (BiO)₂ layer to be insulating with an energy gap of 0.1 eV while the CuO₂ layer was found to be essentially metallic but with an anomalous low-lying excitation spectrum. The modulation structure was observed on the layer-edge surface as well as on the basal plane.