Ultrahigh-resolution photoemission spectroscopy of Ni borocarbides: direct observation of the superconducting gap and a change in gap anisotropy by impurity

T Yokoya; T Kiss; T Watanabe; S Shin; M Nohara; H Takagi; T Oguchi

doi:10.1103/PhysRevLett.85.4952

Ultrahigh-resolution photoemission spectroscopy of Ni borocarbides: direct observation of the superconducting gap and a change in gap anisotropy by impurity

Phys Rev Lett. 2000 Dec 4;85(23):4952-5. doi: 10.1103/PhysRevLett.85.4952.

Authors

T Yokoya¹, T Kiss, T Watanabe, S Shin, M Nohara, H Takagi, T Oguchi

Affiliation

¹ Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.

PMID: 11102159
DOI: 10.1103/PhysRevLett.85.4952

Abstract

We have performed ultrahigh-resolution photoemission spectroscopy of Y(Ni1-xPtx)2B2C ( x = 0.0 and 0.2) in order to study the changes in the density of states across the superconducting transition. Because of a drastic increase in energy resolution, we clearly observe the opening of superconducting gaps across T(c) in both compounds. Furthermore, we find a small but significant difference in the superconducting-state spectral shape. This can be explained in terms of reduction in gap anisotropy by introducing impurities and provides spectroscopic evidence for an anisotropic s-wave gap in YNi2B2C.