Theory of anisotropic s-wave superconductivity with point-node like gap minima: analysis of (Y,Lu)Ni_2B_2C

Abstract

Recent intensive experimental studies revealed that (Y,Lu)Ni${}_2$B${}_2$C is an anisotropic s-wave superconductor. In addition, its gap function possesses deep point minima, whose ratio of the gap anisotropy is more than 10. On the theoretical side, however, it is nontrivial to understand the origin of such a peculiar superconductivity. In the present paper, we propose a mechanism of the s-wave superconductivity with deep gap minima, based on the theoretical model where strong electron-phonon coupling as well as the moderate magnetic fluctuations coexist. By analyzing the strong coupling Eliashberg equation, we find that s-wave superconducting gap function owing to the electron-phonon coupling becomes highly anisotropic as the magnetic fluctuations increases. The set of model parameters for realizing the strong gap anisotropy in the present model will be appropriate for (Y,Lu)Ni${}_2$B${}_2$C. According to the present mechanism, (groups of) pair of gap minima appear at points on the Fermi surface which are connected by the nesting vector $\mathbf{Q}$, in both cases of s-wave superconductors and non s-wave ones. We briefly discuss other superconductors with highly anisotropic gap function, e.g., PrOs${}_4$Sb${}_{12}$ and Na${}_{0.33}$CoO${}_2$.

14 pages

References in corpus (9)

• Time-Reversal Symmetry-Breaking Superconductivity in Heavy Fermion PrOs4Sb12 detected by Muon Spin Relaxation
• Theory of Superconductivity in Strongly Correlated Electron Systems
• Gap Structure of the Spin-Triplet Superconductor Sr2RuO4 Determined from the Field-Orientation Dependence of Specific Heat
• Unconventional Superconductivity and Electron Correlations in Cobalt Oxyhydrate Na${}_{0.35}$CoO${}_2$$\cdot y$H${}_2$O
• Microscopic Identification of the D-vector in Triplet Superconductor Sr_2RuO_4
• 59Co-NMR Knight Shift of the Superconducting NaxCoO2.yH2O
• 59Co-NQR study on superconducting NaxCoO2.yH2O
• A phenomenology for multiple phases in the heavy fermion skutterudite superconductor PrOs4Sb12
• Theory on Superconductivity of CeIn3 in Heavy Fermion System

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