Thermodynamic anisotropy in the samarium-based pnictide single-crystal superconductor
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Thermodynamic anisotropy in the samarium‑based pnictide single‑crystal superconductor A. Pattanaik1 · G. Purohit2 · P. Nayak2 Received: 2 May 2020 / Accepted: 30 June 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract We have studied theoretically the anisotropic properties of Sommerfeld coefficient and the penetration depth for SmFeAsO1−xFx(x = 0.15) single crystal using the modified phenomenological Ginzburg–Landau (GL) theory for multiband superconducting system. The calculated result of the Sommerfeld coefficient wasfound to be close to that of the experimental result as reported in the earlier literature. In addition, the anisotropic ratio of penetration depths was also evaluated and reported in this manuscript and found to be a qualitative result. The successful explanation of the anisotropic properties of single crystal for the S mFeAsO1−xFx(x = 0.15) system implies that this theory can be successfully used for explaining different anisotropy found in the SmFeAsO1−xFx(x = 0.15) compound. Keywords Fe-based superconductors · SmFeAsO1−xFx(x = 0.15) single crystal · Thermodynamic properties · Phenomenological two-band g.l. theory
1 Introduction The initial discovery of superconductivity at temperatures up to 26 K in L aFeAsO1-xFx has been found in a large number of materials whose common structural motif is the presence of FeAs (or FeSe, Te) planes [1–3]. Various families of FeAs-superconductors can be distinguished, most notably the rareearth-1111 materials derived from the original LaFeAsO1-xFx and the 122-family derived from the Ba1-xKxFe2As2 system [4]. Superconductivity arises upon electron or hole-doped system or due to the application of pressure from an antiferromagnetic parent compound. The highest values of transition temperature (Tc) of ~ 56 K were achieved in Sm- and Gd-based 1111-materials [5, 6]. High temperature superconducting systems (HTSCs), particularly, LaFeAsO1-xFx with composition ReFeAsO1-xFx (R = rare earths), have more structural and theoretical importance compared to cuprate superconductors [7]. These compounds have layered tetragonal crystal structure playing an
* A. Pattanaik [email protected] 1
Department of Physics, IGIT, Sarang, Odisha 759 146, India
School of Physics, Sambalpur University, Burla 768 019, India
2
important role in the property of superconductivity [1]. All of the FeAs-based HTSCs contain square lattice layers of Fe atoms, where each Fe atom is at the center of a distorted As tetrahedron forming equiatomic FeAs layer. These FeAs layers are separated by spacer/charge donation layers along the c-axis such as Ba layers in body-centered tetragonal BaFe2As2 or LaO layers in primitive tetragonal LaFeAsO [8–10]. An important thermal property associated with the superconductivity in a material is the jump of change in specific heat in the electronic component close to transition temperature. A nearly discontinuous increase in heat capacity at transition temperature only occur if a sample has a single well-defined transition
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