LOW-TEMPERATURE STUDIES ON NORMAL PEROVSKITE OXIDES - ROLE OF CORRELATION AND DISORDER

In this report we discuss the main results of low temperature transport and tunneling measurements in correlated metallic oxides belonging to the ABO3 class. Electron-electron interaction in these metallic oxides gives rise to a T1/2 term in the conductivity (sigma) below 10 K. The tunneling conductance shows a characteristic cusp. In these materials the metallic state [sigma(T = 0) not-equal 0] is retained for sigma(T = 0) < sigma(Mott) and dsigma/dT > 0. Near the critical region of the metal-insulator transition we find that the conductivity sigma(T) varies as sigma0 + alphaT(m). However, away from the transition, m = 1/2 and as sigma0 < sigma(Mott), m --> 1/3 or 1/2.5 depending on the strength of magnetic scattering. But very close to the transition (sigma0 much less than sigma(Mott)), m --> 1.