Critical temperature and giant isotope effect in presence of paramagnons

O. V. Dolgov; I. I. Mazin; A. A. Golubov; S. Y. Savrasov; E. G. Maksimov

doi:10.1103/physrevlett.95.257003

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Critical temperature and giant isotope effect in presence of paramagnons

O. V. Dolgov·I. I. Mazin·A. A. Golubov·S. Y. Savrasov·E. G. Maksimov

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Abstract

We reconsider the long-standing problem of the effect of spin fluctuations on the critical temperature and isotope effect in a phonon-mediated superconductor. Although the general physics of the interplay between phonons and paramagnons had been rather well understood, the existing approximate formulas fail to describe the correct behavior of $% T_{c}$ for general phonon and paramagnon spectra. Using a controllable approximation, we derive an analytical formula for $T_{c}$ which agrees well with exact numerical solutions of the Eliashberg equations for a broad range of parameters. Based on both numerical and analytical results, we predict a strong enhancement of the isotope effect when the frequencies of spin fluctuation and phonons are of the same order. This effect may have important consequences for near-magnetic superconductors such as MgCNi$_{3}$

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O. V. Dolgov, I. I. Mazin, A. A. Golubov, S. Y. Savrasov, E. G. Maksimov. 2005-06-15. Critical temperature and giant isotope effect in presence of paramagnons. https://doi.org/10.1103/physrevlett.95.257003

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