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Local density of states on rough surfaces of dx2−y2-wave superconductors

Y. Tanuma, Y. Tanaka, M. Yamashiro, S. Kashiwaya

DOI 10.1103/PhysRevB.57.7997 · Physical Review B

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Abstract

The spatial variations of the local density of states (LDOS) on the surface of dx2−y2-wave superconductors are calculated using an extended Hubbard model. Our model has the ability to treat the surface geometry with atomic-scale roughness, and gives realistic results beyond those based on the quasiclassical theory. The spatial variation of the LDOS is obtained for various types of surface geometries using a self-consistently determined pair potential. As surface bound states are peculiar to d-wave superconductors, we pay attention to the appearance of zero-energy states (ZES’s). For a flat surface, the formation of a ZES on a [110] surface and the lack of one on a [100] surface is obtained, which is consistent with the results of the quasiclassical theory. However, the LDOS shows abundant spatial dependence when the surfaces have roughness. The appearance of a ZES on nominal [100] surfaces and its disappearance on nominal [110] surfaces are obtained depending on geometry. The calculations explain the origin of various spectra observed by tunneling spectroscopy on high-Tc superconductors.

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