Josephson effect and Andreev reflection in Ba₁₋xNaxFe₂As₂ (x = 0.25 and 0.35) point contacts

• Published in: Физика низких температур
• Date: 2014
• Main Authors: Fisun, V.V., Balkashin, O.P., Kvitnitskaya, O.E., Korovkin, I.A., Gamayunova, N.V., Aswartham, S., Wurmehl, S., Naidyuk, Yu.G
• Format: Article
• Language: English
• Published: Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України 2014
• Subjects: III Международный семинар по микроконтактной спектроскопии
• Online Access: https://nasplib.isofts.kiev.ua/handle/123456789/119675
• Journal Title: Digital Library of Periodicals of National Academy of Sciences of Ukraine
• Cite this: Josephson effect and Andreev reflection in Ba₁₋xNaxFe₂As₂ (x = 0.25 and 0.35) point contacts / V.V. Fisun, O.P. Balkashin, O.E. Kvitnitskaya, I.A. Korovkin, N.V. Gamayunova, S. Aswartham, S. Wurmehl, Yu.G. Naidyuk // Физика низких температур. — 2014. — Т. 40, № 10. — С. 1175-1181. — Бібліогр.: 24 назв. — англ.

I(V) characteristics and their first derivatives of ScS and ScN-type (S is superconductor, c is constriction, N is
 normal metal) point contacts (PCs) based on Ba₁₋xNaxFe₂As₂ (x = 0.25 and 0.35) were studied. ScS-type PCs with
 S = Nb,Ta, and Pb show Josephson-like resistively shunted I(V) curves with microwave induced Shapiro steps
 which satisfy relation 2eV = ω. The IcRN product (Ic is critical current, RN is normal state PC resistance) in these
 PCs is found to be up to 1.2 mV. All this data with the observed dependence of the Ic on the microwave power of
 ScS PCs with Pb counterelectrode indicates the presence of the singlet s-wave type pairing in Ba₁₋xNaxFe₂As₂.
 From the dV/dI(V) curves of ScN-type PCs demonstrating Andreev-reflection like features, the superconducting gap
 ∆ ratio 2∆/kBTc = 3.6 ± 1 for the compound with x = 0.35 was evaluated. Analysis of these dV/dI(V) at high biases
 V, that is well above ∆, testifies transition to the thermal regime in PCs with a voltage increase.