Samarium hexaboride SmB6 has been since many years
considered to be a typical representative of intermediate valence
semiconductors in which the oxidation state of samarium ions
fluctuates between the Sm2þ (4f6
) and Sm3þ (4f5
e5d1
) configurations,
and as a prime example of a narrow-gap Kondo insulator
[1e3]. More than four decades after the pioneering investigations
of Nickerson et al. [4] a large number of detailed and rather
comprehensive studies of SmB6 have been performed. However,
some fundamental properties of SmB6 such as the electrical
transport mechanism (electrical conductivity) at very low temperatures
are still not fully understood. Experimental investigations
on SmB6 (see e.g. [5e12]) have shown that in the energy spectrum
of this material three energy scales and regimes of low temperature
electron kinetics exist. In the range 70K < T < 15 K the properties of
SmB6 are governed by the hybridization gap Eg z 10e20 meV