A functional renormalization group approach to the Anderson impurity model

作者：Bartosch Lorenz^*; Freire Hermann; Ramos Cardenas Jose Juan; Kopietz Peter

来源：Journal of Physics: Condensed Matter , 2009, 21(30): 305602.

DOI：10.1088/0953-8984/21/30/305602

We develop a functional renormalization group approach which describes the low-energy single-particle properties of the Anderson impurity model up to intermediate on-site interactions U less than or similar to 15 Delta , where Delta is the hybridization in the wide-band limit. Our method is based on a generalization of a method proposed by Schutz et al (2005 Phys. Rev. B 72 035107), using two independent Hubbard-Stratonovich fields associated with transverse and longitudinal spin fluctuations. Although we do not reproduce the exponentially small Kondo scale in the limit U -> infinity, the spin fluctuations included in our approach remove the unphysical Stoner instability predicted by mean field theory for U > pi Delta. We discuss different decoupling schemes and show that a decoupling which manifestly respects the spin-rotational invariance of the problem gives rise to the lowest quasiparticle weight. To obtain a closed flow equation for the fermionic self-energy we also propose a new scheme of truncation of the functional renormalization group flow equations using Dyson-Schwinger equations to express bosonic vertex functions in terms of fermionic ones.

• 出版日期2009-7-29