Multiband superconductivity in SrFe2−xNixAs2

• Published in: SN applied sciences 2022-06, Vol.4 (6), p.1-7, Article 171
• Main Authors: Usoltsev, A. S., Sadakov, A. V., Sobolevskiy, O. A., Vlasenko, V. A., Pervakov, K. S., Polianskaya, E. A., Maltsev, E. I.
• Format: Article
• Language: English
• Subjects: Applied and Technical Physics; Chemistry/Food Science; Earth Sciences; Engineering; Environment; Iron-based superconductors; Materials Science; Research Article; Superconducting energy gaps; Upper critical field
• ISSN: 2523-3963; 2523-3971
• DOI: 10.1007/s42452-022-05047-3

In this paper, we present a detailed study of the upper critical field and the energy gap structure of SrFe 2−x Ni x As 2 single crystals with different nickel doping levels. Superconducting transitions were measured resistively in longitudinal and transverse magnetic fields up to 16T. The anisotropy of the upper critical field H c2 ||ab/H c2 ||c decreases monotonically to 1.4 with decreasing temperature for all measured samples. The WHH model was not able to fit measured H c2 (T) temperature dependences well, but the effective two-band model is in good agreement with the data and anisotropy behavior. Values and temperature dependences of superconducting gaps were determined directly by multiple Andreev reflection spectroscopy on symmetrical SnS junctions. Andreev reflections study revealed two superconducting gaps; our data are in line with the experimental results on most iron-based superconductors. Article highlights We obtained values and temperature dependencies of two distinct energy gaps in SrFe 2−x Ni x As 2 (Sr-122) superconductor. This is important addition to multiband superconductivity studies in Sr-122 system. Upper critical field temperature dependencies in H||c and H||ab orientations are analyzed in terms of two band model.