Surface density of states of s+-wave Cooper pairs in a two-band model

TL;DR

This paper investigates the surface density of states in a two-band superconductor with s+-wave pairing, revealing the presence of Andreev bound states due to sign-changing gaps but no zero-energy peak, indicating complex tunneling spectra.

Contribution

It provides a detailed calculation of SDOS in s+-wave superconductors, highlighting differences from d-wave cases and clarifying the effects of interband sign change.

Findings

Andreev bound states appear at the surface due to sign change in gap functions.

No zero-energy peak of SDOS is observed in s+-wave case.

Surface tunneling spectra are more complex than in d-wave superconductors.

Abstract

We calculate surface density of state (SDOS) of s+-wave Cooper pair in two-band superconductor model, where gap functions have different signs between two bands. We find that Andreev bound state appears at surface due to the sign change in the gap function in the interband quasiparticle scattering. However, we do not obtain the zero-energy peak of SDOS in contrast to the d-wave case. The tunneling spectroscopy of s+-wave is much more complex as compared to the d-wave case realized in high-Tc cuprates.