K. Chen et C. Jayaprakash, THE KONDO EFFECT IN PSEUDO-GAP FERMI SYSTEMS - A RENORMALIZATION-GROUP STUDY, Journal of physics. Condensed matter, 7(37), 1995, pp. 491-498
We present a Wilson renormalization group study of the Kondo problem i
n a pseudo-gap Fermi system with density of states rho(epsilon - epsil
on(F)) = C\epsilon - epsilon(F)\(r). For initial couplings J(0) < J(c)
approximate to -2r the impurity spin is quenched, but we find that th
e model exhibits unusual low-temperature properties unique to pseudo-g
ap systems. For r < 0.5 the ground state is characterized by the J = -
infinity fixed point, with a residual magnetic moment and non-vanishin
g entropy. The magnetic susceptibility is shown to fit the universal c
urve, T-X(T) = r/8 + (1 - r - 3r(2)/2)f(1/2((T/T-K)(1-2r) + (T/T-K)(1-
r))), where f(x) is the universal function for the ordinary Kondo prob
lem. For r > 0.5 we also find the quenching of the impurity spin, yet
there is no Kondo effect exhibited in the total magnetic susceptibilit
y.