Ground state properties of SmB6

Abstract We have studied the ground state properties of the intermediate valence narrow-gap semiconductor SmB 6 by means of point-contact (PC) spectroscopy and specific heat measurements. The density of states derived from PC tunneling spectra could be decomposed into two energy-dependent parts with E g =21 meV and E d =4.5 meV wide gaps, and a finite residual density of states at the Fermi level. The specific heat of SmB 6 is enhanced below about 2 K, more pronounced for the sample with less impurities. This behavior can be attributed to the formation of a coherent state within the residual density of states in the energy gap.