Anderson impurity in pseudo-gap Fermi systems

Abstract

We use the numerical renormalization group method to study an Anderson\nimpurity in a conduction band with the density of states varying as rho(omega)\n\\propto |omega|^r with r>0. We find two different fixed points: a local-moment\nfixed point with the impurity effectively decoupled from the band and a\nstrong-coupling fixed point with a partially screened impurity spin. The\nspecific heat and the spin-susceptibility show powerlaw behaviour with\ndifferent exponents in strong-coupling and local-moment regime. We also\ncalculate the impurity spectral function which diverges (vanishes) with\n|omega|^{-r} (|\\omega|^r) in the strong-coupling (local moment) regime.\n