Local electronic density of states near steps on the c-plane of Bi 2Sr 2CaCu 2O x studied using low temperature scanning tunneling spectroscopy and microscopy

Abstract

The local electronic density of states near steps on the c-plane of Bi 2Sr 2CaCu 2O x running along the [110] direction in the CuO 2 plane was measured by low temperature scanning tunneling spectroscopy and microscopy. The electronic states were found to be insulating near a step edge on the upper terrace and an insulator–superconductor boundary was formed 7 nm away from the step edge. The superconducting tunneling spectra on the upper terrace depend on the distance from the boundary and the tunneling conductance inside the superconducting gap increases in the region of 10 nm from the boundary. It is speculated that the changes of the superconducting spectra are due to the boundary effects of d x 2−y 2 -wave superconductors.