Screened moments and extrinsic in-gap states in samarium hexaboride

Abstract : Samarium hexaboride (SmB$_6$) 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$_6$, 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 $^{154}$Sm$^{11}$B$_6$ 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$_6$.
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Submitted on : Tuesday, September 25, 2018 - 11:46:23 AM
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W. Fuhrman, J. Chamorro, P. Nikolić, T. Mcqueen, Broholm C.L., et al.. Screened moments and extrinsic in-gap states in samarium hexaboride. Nature Communications, Nature Publishing Group, 2018, 9, pp.1539. ⟨10.1038/s41467-018-04007-z⟩. ⟨cea-01880885⟩



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