title: Superconductivity induced by longitudinal ferromagnetic fluctuations in UCoGe.
abstract: From detailed angle-resolved NMR and Meissner measurements on a ferromagnetic (FM) superconductor UCoGe (T(Curie)∼2.5  K and T(SC)∼0.6  K), we show that superconductivity in UCoGe is tightly coupled with longitudinal FM spin fluctuations along the c axis. We found that magnetic fields along the c axis (H∥c) strongly suppress the FM fluctuations and that the superconductivity is observed in the limited magnetic-field region where the longitudinal FM spin fluctuations are active. These results, combined with model calculations, strongly suggest that the longitudinal FM spin fluctuations tuned by H∥c induce the unique spin-triplet superconductivity in UCoGe. This is the first clear example that FM fluctuations are intimately related with superconductivity.
authors.affiliation: Department of Physics, Graduate School of Science, Kyoto University, Kyoto, Japan. t.hattori@scphys.kyoto-u.ac.jp
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authors.lastname: Hattori
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authors.lastname: Ihara
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authors.lastname: Nakai
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authors.lastname: Ishida
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authors.lastname: Fujimoto
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authors.lastname: Kawakami
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authors.lastname: Deguchi
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authors.lastname: Satoh