Origin of zero-bias conductance peaks in high-Tcsuperconductors

Abstract

A wide variety of experimental conductance spectra in high-${\mathit{T}}_{\mathit{c}}$ superconductors can be explained by a theory of proximity-electron-tunneling spectroscopy (PETS) for d-wave superconductors. From a solution of the Bogoliubov–de Gennes equation, the conductance spectra of the PETS are proved to show gap or zero-bias peak structures depending on the axis orientation of the superconductor. The features of the calculated spectra are consistent with the experimental results of ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ observed by low-temperature scanning tunneling spectroscopy.