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Point-contact Spectroscopy of Superconductors

Transistors – From Point Contact to Single Electron

The first solid state electron device was the metal-semiconductor rectifier discovered by Ferdinand Braun in 1874 even before the discovery of the electron! He found that mercury metal contacts on copper or iron sulphide gave non-linear currentvoltage characteristics. In 1904 J C Bose obtained a U.S patent for point contact rectifiers on Galena (PbS). He found that the direction of rectificatio...

Point-Contact Andreev-Reflection Spectroscopy in Fe-Based Superconductors: Multigap Superconductivity and Strong Electron–Boson Interaction

We performed point-contact Andreev-reflection measurements in Ba(Fe1−xCox)2As2 single crystals (x = 0.1, Tc = 24.5 K) and SmFeAsO1−xFx polycrystals (x = 0.2, Tc = 52 K). The spectra indicate the presence of two superconducting gaps with no line nodes on the Fermi surface, but also feature additional structures related to the electron–boson interaction (EBI). From the spectra, it is possible to ...

Point-contact Spectroscopy of Magnesium Diboride with Different Counter-electrodes

We report on tunneling and Andreev-reflection conductance spectra of 39 K superconducting magnesium diboride, obtained with Pb and Au counter-electrodes. Two distinct steps at close to 2.7 and 7.1 meV appear in a low-resistance metallic-type Au-MgB2 junction characteristic, whereas a tunneling-like spectrum measured for the same junction, annealed by the application of dc current, exhibits only...

Point-contact Spectroscopy of the Nickel Borocarbide Superconductors

An overview of the recent efforts in point-contact (PC) spectroscopy of the nickel borocarbide superconductors RNi2B2C in the normal and superconducting (SC) state is given. The results of measurements of the PC electronboson(phonon) interaction spectral function are presented. Phonon maxima and crystalline-electric-field (CEF) excitations are observed in the PC spectra of compounds with R=Dy, ...