heterostructures

Following a 2010 prediction that the anomalous low-temperature conduction in the Kondo insulator SmB₆ is due to a topological surface state, making SmB₆ the first topological Kondo insulator, a flurry of experimental efforts have produced promising but often inconsistent or contradictory characterizations. While a number of recent studies have attempted to harmonize these results, many experimental discrepancies remain unresolved. Here, we investigate via time domain terahertz spectroscopy the AC conduction of SmB₆ thin films and heterostructures of SmB₆ and the superconductor YB₆. The conduction of SmB₆ thin films is found to be accurately described by a two-channel model of surface and bulk states while the heterostucture conduction concords with the Mattis-Bardeen formalism of BCS superconductivity. These results support the existence of surface conducting states in SmB₆ susceptible to the superconducting proximity effect.