Light scattering from gap excitations and bound states in SmB6

Gap formation and in-gap bound states are investigated in SmB6 using Raman scattering. Below 70 K, we observe an abrupt suppression of electronic scattering below 290 cm-1 that is not consistent with the predicted temperature dependence of a hybridization gap. We also find that gap formation in SmB6 is associated with the appearance of a sharp Eg(3+) symmetry 130-cm-1 excitation. We discuss several possible interpretations of this excitation, including a 7-8 crystal-field transition and a transition between bound 4f55d configurations.