Superconductivity of centrosymmetric and non-centrosymmetric phases in antiperovskite (Ca,Sr)Pd3P

JOURNAL OF ALLOYS AND COMPOUNDS

卷:882

Article

Iyo, Akira¹  Hase, Izumi¹  Fujihisa, Hiroshi¹  Gotoh, Yoshito¹  Takeshita, Nao¹  Ishida, Shigeyuki¹  Ninomiya, Hiroki¹  Yoshida, Yoshiyuki¹  Eisaki, Hiroshi¹  Hirose, Hishiro T.²  Terashima, Taichi²  Kawashima, Kenji^1,3 

[1] Natl Inst Adv Ind Sci & Technol, 1-1-1 Umezono, Tsukuba, Ibaraki 3058568, Japan

[2] Natl Inst Mat Sci, Tsukuba, Ibaraki 3050003, Japan

[3] IMRA JAPAN Co Ltd, 2-36 Hachiken Cho, Kariya, Aichi 4488650, Japan

关键词: Antiperovskite;    Superconductor;    Non-centrosymmetric space group;    Superconducting property;    Electronic band structure;   

DOI  :  10.1016/j.jallcom.2021.160733

来源: Elsevier

【 摘 要 】

In the recently discovered antiperovskite phosphide (Ca,Sr)Pd3P, centrosymmetric (CS) and non-centrosymmetric (NCS) superconducting phases appear depending on the Sr concentration, and their transition temperatures (T-c) differ by as much as one order of magnitude. In this study, we investigated the superconducting properties and electronic band structures of CS orthorhombic (CSo) (Ca0.6Sr0.4)Pd3P (T-c = 3.5 K) and NCS tetragonal (NCSt) (Ca0.25Sr0.75)Pd3P (T-c = 0.32 K) samples with a focus on explaining their large T-c difference. Specific heat measurements indicated that CSo (Ca0.6Sr0.4)Pd3P was an s-wave superconductor in a moderate-coupling regime with a 2 Delta(0)/k(B)T(c) value of 4.0. Low-lying phonons leading to the strong coupling in the structurally analogous SrPt3P were unlikely to be present in CSo (Ca0.6Sr0.4)Pd3P. Given that CSo (Ca0.6Sr0.4)Pd3P and NCSt (Ca0.25Sr0.75)Pd3P exhibited similar Debye temperatures (Theta(D)) of approximately 200 K, the large T-c difference could not be attributed to Theta(D). T-c of each phase was accurately reproduced based on the Bardeen-Cooper-Schrieffer (BCS) theory using experimental data and the density of states of the Fermi level N(0) calculated from their band structures. We concluded that the considerable suppression of T-c in NCSt (Ca0.25Sr0.75)Pd3P can be primarily attributed to the decrease in N(0) associated with the structural phase transition without considering the lack of inversion symmetry. (C) 2021 Elsevier B.V. All rights reserved.

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