Sa. Nemov et al., SUPERCONDUCTIVITY IN THE PBTE-SNTE-GETE SYSTEM WITH IN AND TL QUASI-LOCAL IMPURITY STATES, Czechoslovak journal of Physics, 46, 1996, pp. 863-864
Superconducting (SC) materials based on A(IV)B(VI) solid solutions wit
h deep impurity resonant states of group III elements (In, Tl) was inv
estigated. It was shown that the necessary conditions for the appearan
ce of SC with T-c>lK are: i) the Fermi level is placed in an impurity
band; ii) impurity states are situated near the additional valence ban
d extremum with the high density of states (the Sigma- extremum in mat
erials based on PbTe:Tl and the Sigma- or Delta- extremum in materials
based on SnTe:In). On the other hand, in the case of (Sn1-zGez)(1-x)I
nxTe the changes of the band structure and the impurity band position
may be caused by a structural phase transition observed by resistivity
, Hall-effect, X-ray and magnetization measurements.