A model for critical current effects in point-contact Andreev-reflection spectroscopy

Abstract

It is well known that point-contact Andreev reflection spectroscopy provides reliable measurements of the energy gap(s) in a superconductor when the contact is in the ballistic or nearly-ballistic regime. However, especially when the mean free path of the material under study is small, obtaining ballistic contacts can be a major challenge. One of the signatures of a Maxwell contribution to the contact resistance is the presence of "dips" in the differential conductance, associated to the sudden appearance of a Maxwell term, in turn due to the attainment of the critical current of the material in the contact region. Here we show that, using a proper model for the $R(I)$ of the material under study, it is possible to fit the experimental curves (without the need of normalization) obtaining the correct values of the gap amplitudes even in the presence of such dips, as well as the temperature dependence of the critical current in the contact. We present a test of the procedure in the case of Andreev-reflection spectra in Mg${}_{0.85}$Al${}_{0.15}$B${}_2$ single crystals.

arXiv comment7 pages, 5 figures

References in corpus (10)

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Cited by in corpus (3)

• Superconductivity of Co-Doped CaKFe4As4 Investigated via Point-Contact Spectroscopy and London Penetration Depth Measurements
• Direct evidence for two-gap superconductivity in hydrogen-intercalated titanium diselenide
• Andreev-reflection spectroscopy of SrPt3P single crystals