B solid-state nuclear magnetic resonance*

The strongly-correlated and mixed valence Kondo insulator SmB6 has been shown to exhibit surface states, which are suggested to originate with non-trivial topology. The surface state conduction is observed to dominate over bulk conduction only at Li-He temperatures. However, recently reported results from transport measurements were interpreted as evidence for surface-dominated transport to temperatures as high as 240 K, consistent with a much larger bulk gap. ¹¹B NMR relaxation measurements were carried out under strained conditions, as a means for studying at a microscopic level the gap evolution, and in search for evidence of a heterogeneous phase. In initial measurements, the behavior is consistent with a 50% increase in energy gap with only 0.5% uniaxial strain; experiments at higher strain are underway.