Multiband coupling effect on splitting of zero-bias conductance peak of (1 1 0) surface states in [formula omitted

Abstract

The electronic density of states (DOS) of (110) surface states in an YBCO high temperature superconductor were theoretically studied within a two-band approach for a semi-infinite-thickness film. As the conducting chain and plane layers in the material exhibit the superconductivity, the dispersions of those layers were taken into account, and modeled by the tight-binding bands under consideration to the second next nearest neighbor state. The impact of the chain-plane coupling strength was investigated in the calculation. The model parameters were extracted from the photoemission experiments. For comparison, the superconducting order parameter was modeled either dx2-y2 or dx2-y2+Δs, where Δs is the s-wave component. It was found that the zero-bias conductance peak of the plane layer in the case of dx2-y2+Δs order parameter can immediately split even if there is no coupling strength between the bands. However, in another case, this peak splits into two peaks with the presence of the coupling strength. Particularly, the splitting of the peak strongly depends on the size of the coupling strength.