Superconducting energy gap distribution in c-axis oriented MgB\(_2\) thin film from point contact study

• Published in: arXiv.org 2002-03
• Main Authors: Naidyuk, Yu G, Yanson, I K, Tyutrina, L V, Bobrov, N L, Chubov, P N, Kang, W N, Hyeong-Jin, Kim, Choi, Eun-Mi, Sung-Ik, Lee
• Format: Article
• Language: English
• Subjects: Differential thermal analysis; Energy distribution; Energy gap; Fermi surfaces; Histograms; Point contact; Qualitative analysis; Silver; Superconductivity; Thin films
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.0112452

We have analyzed about 100 voltage-dependent differential resistance dV/dI(V) curves of metallic point contacts between c-axis oriented MgB\(_2\) thin film and Ag, which exhibit clear Andreev reflection features connected with the superconducting gap. About one half of the curves show the presence of a second larger gap. The histogram of the double-gap distribution reveals distinct maxima at 2.4 and 7 meV, while curves with a single-gap features result in more broad maximum at 3.5 meV. The double-gap distribution is in qualitative agreement with the distribution of gap values over the Fermi surface calculated by H. J. Choi et al. (cond-mat/0111183). The data unequivocally show the presence of two gaps \(\Delta_{S}=2.45\pm 0.15\) meV and \(\Delta_{L}=7.0\pm 0.45\) meV in MgB\(_2\) with gap ratio \(2.85\pm 0.15\). Our observations prove further a widely discussed multi-gap scenario for MgB\(_2\), where two distinct gaps are seen in the clean limit, while a single averaged gap is present in the dirty one.