A calorimetric investigation of RbFe₂As₂ single crystals

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• 作者：Seunghyun Khim ; Saicharan Aswartham ; Vadim Grinenko ; Dmitry Efremov ; Christian G. F. Blum ; Frank Steckel ; Daniel Gruner ; Anja U. B. Wolter ; Stefan-Ludwig Drechsler ; Christian Heß ; Sabine Wurmehl and Bernd Bü ; chner
• 刊名：physica status solidi (b)
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：254
• 期：1
• 全文大小：625K
• ISSN：1521-3951

文摘

We present properties of single crystals of the iron pnictide superconductor RbFe₂As₂ grown using a self-flux method. A bulk superconducting transition at Tc ∼2.6 K was consistently observed in resistivity, magnetic susceptibility, and specific heat measurements. While the resistivity behaves like a conventional metal at low T, the magnetic susceptibility shows an unusual broad maximum around 80 K in the normal state. A large Sommerfeld coefficient, γ0=127mJ/mol K2, was observed seemingly a common feature of heavily hole-doped “122” compounds. In the superconducting state, we analyzed our specific heat data based on the s- and d-wave two-gap models. The presence of the small gap with 2Δ1(0)/kBTc<1 was discussed to account for the large specific heat contribution remaining to low T far below Tc. The large Hc2 anisotropy ratio, ΓH = Hc2ab/Hc2c ∼ 7 near Tc indicates that the large gap would occupy a highly two-dimensional Fermi surface.