Andreev-reflection spectroscopy with superconducting indium — a case study

• Published in: Физика низких температур
• Date: 2013
• Main Authors: Gloos, K., Tuuli, E.
• Format: Article
• Language: English
• Published: Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України 2013
• Subjects: К 75-летию со дня рождения И. К. Янсона
• Online Access: https://nasplib.isofts.kiev.ua/handle/123456789/118224
• Journal Title: Digital Library of Periodicals of National Academy of Sciences of Ukraine
• Cite this: Andreev-reflection spectroscopy with superconducting indium — a case study / K. Gloos, E. Tuuli // Физика низких температур. — 2013. — Т. 39, № 3. — С. 326–334. — Бібліогр.: 51 назв. — англ.

We have investigated Andreev reflection at interfaces between superconducting indium (Tc = 3.4 K) and several normal conducting nonmagnetic metals (palladium, platinum, and silver) down to T = 0.1 K as well as zinc (Tc = 0.87 K) in its normal state at T = 2.5 K. We analyzed the point-contact spectra with the modified onedimensional BTK theory valid for ballistic transport. It includes Dynes’ quasiparticle lifetime as fitting parameter Γ in addition to superconducting energy gap 2Δ and strength Z of the interface barrier. For contact areas from less than 1 nm² to 10000 nm² the BTK Z-parameter was close to 0.5, corresponding to transmission coefficients of about 80%, independent of the normal metal. The very small variation of Z indicates that the interfaces have a negligible dielectric tunneling barrier. Also Fermi surface mismatch does not account for the observed Z. The extracted value Z ≈ 0.5 can be explained by assuming that practically all of our point contacts are in the diffusive regime.