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arXiv · 1705.09885

Breakdown of single spin-fluid model in heavily hole-doped superconductor CsFe2As2

D. Zhao·S. J. Li·N. Z. Wang·J. Li·D. W. Song·L. X. Zheng·L. P. Nie·X. G. Luo·T. Wu·X. H. Chen
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Abstract

Although Fe-based superconductors are multiorbital correlated electronic systems, previous nuclei magnetic resonance (NMR) measurement suggests that a single spin-fluid model is sufficient to describe its spin behavior. Here, we firstly observed the breakdown of single spin-fluid model in a heavily hole-doped Fe-based superconductor CsFe2As2 by site-selective NMR measurement. At high temperature regime, both of Knight shift and nuclei spin-lattice relaxation at 133Cs and 75As nuclei exhibit distinct temperature-dependent behavior, suggesting the breakdown of single spin-fluid model in CsFe2As2. This is ascribed to the coexistence of both localized and itinerant spin degree of freedom at 3d orbits, which is consistent with orbital-selective Mott phase. However, single spin-fluid behavior is gradually recovered by developing a coherent state among 3d orbits with decreasing temperature. A Kondo liquid scenario is proposed for the low-temperature coherent state. The present work sets strong constraint on the theoretical model for Fe-based superconductors.

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D. Zhao, S. J. Li, N. Z. Wang, J. Li, D. W. Song, L. X. Zheng, L. P. Nie, X. G. Luo, T. Wu, X. H. Chen. 2017-05-28. Breakdown of single spin-fluid model in heavily hole-doped superconductor CsFe2As2. https://doi.org/10.1103/physrevb.97.045118

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