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Screened Moments and Extrinsic In-Gap States in Samarium Hexaboride



W. T. Fuhrman, J. R. Chamorro, P. A. Alekseev, J.-M. Mignot, T. Keller, Jose Rodriguez Rivera, Yiming Qiu, P. Nikolic, T. M. McQueen, Collin L. Broholm


The Kondo impurity effect in metals is the result of quantum-mechanical scattering of conduction electrons by magnetic impurities.1 This process leads to exotic effects such as unconventional superconductivity and an effective electron mass enhanced by 2-3 orders of magnitude. 2-3 The small bandgap insulator SmB6 has long been known to have thermodynamic properties at odds with being an insulator, yet the extensive search for low-enery phenomena which could explain this has remained elusive and controversial even after 50 years of research into its unconventional nature. 4-9 We have observed a Kondo impurity-like momnet screening effect in the insulating state of nominally pure and Gd-doped SmB6 via heat capacity, magnetization, and resistivity measurements. High-resolution neutron scattering on the low energy regime confirms directly that no coherent magnetism is evident below the long-lived 13 meV spin exciton, restricting proposals of intrinsic neutral low-energy magnetic excitations. 10-12 We infer that the mixed valence, strongly-correlated nature of SmB6 exhibits extreme sensitivity to impurities and defects which induce metal-like bulk properties. The requisite interactions leading to this effect are not unique to SmB6, suggesting this phenomena may provide an understanding of metallic properties in other correlated insulators. 13
Nature Communications


Neutron Scattering, magnetic materials, superconductivity.


Fuhrman, W. , Chamorro, J. , Alekseev, P. , Mignot, J. , Keller, T. , Rodriguez Rivera, J. , Qiu, Y. , Nikolic, P. , McQueen, T. and Broholm, C. (2018), Screened Moments and Extrinsic In-Gap States in Samarium Hexaboride, Nature Communications, [online], (Accessed April 16, 2024)
Created April 17, 2018, Updated October 12, 2021