Mott physics and collective modes: an atomic approximation of the four-particle irreducible functional

Thomas Ayral (1) , Olivier Parcollet (1)

1 IPHT - Institut de Physique Théorique - UMR CNRS 3681

We discuss a generalization of the dynamical mean field theory (DMFT) for strongly correlated systems close to a Mott transition based on a systematic approximation of the fully irreducible four-point vertex. It is an atomic-limit approximation of a functional of the one- and two-particle Green functions, built with the second Legendre transform of the free energy with respect to the two-particle Green function. This functional is represented diagrammatically by four-particle irreducible (4PI) diagrams. Like the dynamical vertex approximation (D$\Gamma$A), the fully irreducible vertex is computed from a quantum impurity model whose bath is self-consistently determined by solving the parquet equations. However, in contrast with D$\Gamma$A and DMFT, the interaction term of the impurity model is also self-consistently determined. The method interpolates between the parquet approximation at weak coupling and the atomic limit, where it is exact. It is applicable to systems with short-range and long-range interactions.

Mots clés: cond-mat

Domaines: Physique [physics]

Thomas Ayral, Olivier Parcollet. Mott physics and collective modes: an atomic approximation of the four-particle irreducible functional. 2016. ⟨cea-01341620v1⟩