Abstract
The controversial ground-state properties of the Kondo insulator have been investigated using NMR in very high magnetic fields up to . We find evidence that, following the development of a gap in the conduction-band density of states below , the in-gap states dominate the nuclear relaxation at temperatures less than . The Korringa product exhibits anomalous behavior in this range and the application of high magnetic fields leads to suppression of nuclear relaxation. The hybridization gap, however, remains open up to . The behavior of the relaxation at low temperatures suggests a strong field dependence of the in-gap states and rules out the possibility that bound states arise from vacancies. A simple density-of-states model and a band scheme are introduced to account for these observations.
- Received 25 September 2006
DOI:https://doi.org/10.1103/PhysRevB.75.075106
©2007 American Physical Society