Spin-Triplet Superconductivity Induced by Longitudinal Ferromagnetic Fluctuations in UCoGe: Theoretical Aspect

10th International Conference on Materials and Mechanisms of Superconductivity

Tada, Y.^1 ; Fujimoto, S.^2 ; Kawakami, N.^2 ; Hattori, T.^2 ; Ihara, Y.^3 ; Ishida, K.^2 ; Deguchi, K.^4 ; Sato, N.K.^4 ; Satoh, I.^5

Institute for Solid State Physics, University of Tokyo, Chiba 277-8581 Kashiwa, Japan^1

Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan^2

Department of Physics, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan^3

Department of Physics, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan^4

Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan^5

关键词: Conventional superconductors;    Eliashberg equations;    Ferromagnetic fluctuation;    Isotopic substitution;    Magnetic fluctuation;    Unconventional superconductivity;    Unconventional superconductors;    Upper critical magnetic fields;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/449/1/012029/pdf
DOI  :  10.1088/1742-6596/449/1/012029

来源: IOP

【 摘 要 】

Identification of pairing mechanisms leading to the unconventional superconductivity realized in copper-oxide, heavy-fermions, and organic compounds is one of the most challenging issues in condensed-matter physics. Clear evidence for an electron-phonon mechanism in conventional superconductors is seen by the isotope effect on the superconducting transition temperatures TSC, since isotopic substitution varies the phonon frequency without affecting the electronic states. In unconventional superconductors, magnetic fluctuations have been proposed to mediate superconductivity, and considerable efforts have been made to unravel relationships between normal-state magnetic fluctuations and superconductivity. Here, we show that characteristic experimental results on the ferromagnetic (FM) superconductor UCoGe (TCurie ∼ 2.5 K and TSC ∼ 0.6 K) can be understood consistently within a scenario of the spin-triplet superconductivity induced by FM spin fluctuations. Temperature and angle dependencies of the upper critical magnetic field of the superconductivity (Hc2) are calculated on the basis of the above scenario by solving the Eliashberg equation. Calculated Hc2 well agrees with the characteristic experimental results observed in UCoGe. This is a first example that FM fluctuations are shown to be a pairing glue of superconductivity.