Screened moments and extrinsic in-gap states in samarium hexaboride.

Author(s) Fuhrman, W.T.; Chamorro, J.R.; Alekseev, P.A.; Mignot, J.M.; Keller, T.; Rodriguez-Rivera, J.A.; Qiu, Y.; Nikolić, P.; McQueen, T.M.; Broholm, C.L.
Journal Nat Commun
Date Published 2018 Apr 18
Abstract

Samarium hexaboride (SmB) is a Kondo insulator, with a narrow gap due to hybridization between localized and conduction electrons. Despite being an insulator, many samples show metal-like properties. Rare-earth purification is exceedingly difficult, and nominally pure samples may contain 2% or more of impurities. Here to determine the effects of rare-earth doping on SmB, we synthesized and probed a series of gadolinium-doped samples. We found a relationship between specific heat and impurity moment screening which scales systematically. Consistent with this finding, our neutron scattering experiments of a high purity sample of doubly isotopic SmB show no intrinsic excitations below the well-established 13 meV spin-exciton. The result of introducing impurities into a Kondo insulator is incompletely understood, but it is clear from our measurements that there is a systematic relationship between rare-earth impurities and metal-like properties in SmB.

DOI 10.1038/s41467-018-04007-z
ISSN 2041-1723
Citation Fuhrman WT, Chamorro JR, Alekseev PA, Mignot J-, Keller T, Rodriguez-Rivera JA, et al. Screened moments and extrinsic in-gap states in samarium hexaboride. Nat Commun. 2018;9(1):1539.

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