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

We calculate the 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 the 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.