Multiple Andreev Reflection Effect Spectroscopy of Underdoped NaFe1 – xCoxAs Single Crystals

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Abstract

We study the structure of the superconducting order parameter in underdoped NaFe1 – xCoxAs pnictides with Tc ≈ 19–21 K related to the 111 family. Using incoherent multiple Andreev reflection effect spectroscopy of planar break junctions, we directly determine the magnitudes of the two microscopic superconducting order parameters: the small superconducting gap ΔS(0), and possible edges of the large gap ΔL(0) having an anisotropy in the 
 plane at T ≪ Tc, the corresponding characteristic ratios, as well as their temperature dependences. Additionally, we detect features of the tunneling spectra in NaFe1 – xCoxAs at 
, those irrelative to superconducting state, and discuss their origin.

About the authors

S. A Kuz'michev

Lebedev Physical Institute, Russian Academy of Sciences, 119991, Moscow, Russia; Faculty of Physics, Moscow State University, 119991, Moscow, Russia

Email: kuzmichevate@lebedev.ru

I. V Morozov

Faculty of Chemistry, Moscow State University, 119991, Moscow, Russia

Email: kuzmichevate@lebedev.ru

A. I Shilov

Lebedev Physical Institute, Russian Academy of Sciences, 119991, Moscow, Russia

Email: kuzmichevate@lebedev.ru

E. O Rakhmanov

Lebedev Physical Institute, Russian Academy of Sciences, 119991, Moscow, Russia; Faculty of Chemistry, Moscow State University, 119991, Moscow, Russia

Email: kuzmichevate@lebedev.ru

T. E Kuz'micheva

Lebedev Physical Institute, Russian Academy of Sciences, 119991, Moscow, Russia

Author for correspondence.
Email: kuzmichevate@lebedev.ru

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