The relaxation rate in Nb-doped strontium titanate involving different
scattering channels is investigated theoretically. It is demonstrated that the
total relaxation rate in SrTiO_{3} is provided mainly by two mechanisms. The
Baber electron-electron scattering with participation of both Coulomb and
phonon-mediated electron-electron interactions provides the T^{2}-dependence of
the relaxation rate. The scattering on the potential landscape caused by
impurities is responsible for the residual relaxation rate at low temperatures.
A good agreement with experiment is achieved accounting for all phonon branches
in strontium titanate, both the optical and acoustic phonons. It is shown that
the effective electron-electron interaction can be attractive in strontium
titanate, and provides superconductivity at low temperatures and Fermi-liquid
response in a wide range of temperatures. Thus our microscopic model supports
the notion that superconductivity and Fermi-liquid properties of n-type
SrTiO_{3} have a common origin.Comment: 22 pages, 6 figures, 1 tabl
