Consequences of the local spin self-energy approximation on the heavy-fermion quantum phase transition

We show, using the periodic Anderson model, that the local spin self-energy approximation, as implemented in the extended dynamical mean field theory (EDMFT), results in a first-order phase transition that persists to T=0. Around the transition, there is a finite coexistence region of the paramagnetic and antiferromagnetic (AFM) phases. The region is bounded by two critical transition lines that differ by an electron-hole bubble at the AFM ordering wave vector.