Low Temperature Physics: 39, 252 (2013); https://doi.org/10.1063/1.4794999 (7 pages)
Физика Низких Температур: Том 39, Выпуск 3 (Март 2013), c. 326-334    ( к оглавлению , назад )

Andreev-reflection spectroscopy with superconducting indium - a case study

Kurt Gloos

Wihuri Physical Laboratory, Department of Physics and Astronomy, University of Turku, FIN-20014 Turku, Finland
Turku University Centre for Materials and Surfaces (MatSurf), FIN-20014 Turku, Finland
E-mail: kgloos@utu.fi

Elina Tuuli

Wihuri Physical Laboratory, Department of Physics and Astronomy, University of Turku, FIN-20014 Turku, Finland

The National Doctoral Programme in Nanoscience (NGS-NANO), FIN-40014 University of Jyväskylä, Finland

Received October 29, 2012

Аннотация

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.

PACS: 85.30.Hi Surface barrier, boundary, and point contact devices;
PACS: 73.40.–c Electronic transport in interface structures;
PACS: 74.45.+c Proximity effects; Andreev reflection; SN and SNS junctions.

Ключевые слова: point contacts, metal interfaces, normal reflection, Andreev reflection.