Realistic manybody approach to materials with strong nonlocal correlations
Our project aims at substantial progress in the development of a realistic dynamical
meanfield theory. This is achieved by advancing our presentday impurity solvers and
by improving the interface to band theory. We employ optimized quantum MonteCarlo techniques for
the numerical evaluation of the recently developed dualfermion approach which is
extended for a general impurity model with several orbitals and sites.
Our goal is to include nonlocal correlations beyond the singlesite DMFT, to include
long wavelength modes and to calculate dynamical twoparticle correlation functions.
These finitetemperature (T>0) methods are checked against a T=0 solver that will be developed by
using a recent reformulation of the (dynamical) densitymatrix renormalization group
in terms of matrixproduct states. The prime goal is to provide and apply a T=0
multiorbital impurity solver without a sign problem and for real frequencies.
Vital methodical progress is
envisaged at the interface of DMFT to effective singleparticle methods: This
comprises tailored basis sets for an efficient representation of the correlated
subspace, global charge selfconsistency as well as access to phase diagrams and atomic
forces due to a reliable scheme to compute the free energy. Correlated transition
metals and compounds as well as correlationinduced insulators and frustrated lattice
systems are considered.
