Effect of valence fluctuations on the ground state properties of SmB6
  We argue that because of valence-fluctuation caused dynamical changes (fluctuations) of impurity energies in the impurity band of SmB6, energies of electrons occupying impurity sites can be due to the uncertainty principle only estimated with corresponding uncertainty, so they can be represented by energy intervals of non-zero width. As a conse- quence, both occupied as well as unoccupied states can be found in the impurity band above as well as below Fermi level even in the ground state. Therefore the subsystem of localized charge carriers in the ground state of SmB6 cannot be described by an energy distribution function expected for T = 0 K. This fundamental conclusion adds another reason for absence of resistivity divergence in SmB6 at lowest temperatures, and sheds new light on interpretation of experimental data obtained for SmB6 and similar systems at lowest temperatures. 
M. Batkova and I. Batko
cond-mat.str-el