Suppressed coherence due to orbital correlations in the ferromagnetically ordered metallic phase of Mn compounds

Small Drude weight D together with small specific heat coefficient gamma observed in the ferromagnetic phase of R(1-x)A(x)MnO(3) (R = La, Pr, Nd, Sm; A = Ca; Sr, Ba) are analyzed in terms of a proximity effect of the Mott insulator. The scaling theory for the metal-insulator transition with the critical enhancement of orbital correlations toward the staggered ordering of two e(g) orbitals such as 3x(2) - r(2) and 3y(2) - r(2) symmetries may lead to the critical exponents of D proportional to delta(u) and gamma proportional to delta(v) with u = 3/2 and v = 0. The result agrees with the experimental indications.