Unconventional superconductivity from heavy fermion (HF) is always observed in f-electron systems, in which Kondo physics between localized f-electrons and itinerant electrons plays an essential role. Whether HF superconductivity could be achieved in other systems without f electrons, especially for d-electron systems, is still elusive. Here, we experimentally study the origin of d-electron HF behavior in iron-based superconductors (FeSCs) AFe2As2 (A = K, Rb, Cs). Nuclear magnetic resonance on 75As reveals a universal coherent-incoherent crossover with a characteristic temperature T*. Below T*, a so-called 'Knight shift anomaly' is first observed in FeSCs, which exhibits a scaling behavior similar to f-electron HF materials. Furthermore, the scaling rule also regulates the manifestation of magnetic fluctuation. These results undoubtedly support an emergent Kondo scenario for the d-electron HF behavior, which suggests the AFe2As2 (A = K, Rb, Cs) as the first material realization of d-electron HF superconductors.
@article{arxiv.1507.08732,
title = {Emergent Kondo scaling in iron-based superconductors AFe2As2 (A = K, Rb, Cs)},
author = {Y. P. Wu and D. Zhao and A. F. Wang and N. Z. Wang and Z. J. Xiang and X. G. Luo and T. Wu and X. H. Chen},
journal= {arXiv preprint arXiv:1507.08732},
year = {2016}
}
Comments
15 pages, 4 figures, including supplementary information with 9 figures