We study the new binary intermetallic superconductor MgB2 using high-resolution photo-emission spectroscopy. The superconducting-state spectrum measured at 5.4 K shows a coherent peak with a shoulder structure, in sharp contrast to that expected from a simple isotropic-gap opening. The spectrum can be well reproduced using the weighted sum of two Dynes functions with the gap sizes of 1.7 and 5.6 meV. Temperature-dependent study shows that both gaps close at the bulk transition temperature. These results provide spectroscopic evidence for a multiple gap of MgB2.
@article{arxiv.cond-mat/0104489,
title = {Direct evidence for a multiple superconducting gap in MgB2 from high-resolution photoemission spectroscopy},
author = {S. Tsuda and T. Yokoya and T. Kiss and Y. Takano and K. Togano and H. Kitou and H. Ihara and S. Shin},
journal= {arXiv preprint arXiv:cond-mat/0104489},
year = {2009}
}
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4 pages in RevTeX format (3 Figures) submitted to PRL