Аннотация:
We formulate a general cluster Dual Fermion Approach to nonlocal correlations in crystals. The scheme
allows the treatment of long-range correlations beyond the cluster DMFT and nonlocal effects in realistic
calculations of multiorbital systems. We show that the simplest approximation exactly corresponds to the freecluster DMFT. We apply this approach to the one-dimensional Hubbard model. Already the first dual-fermion
correction to the free cluster leads to a drastic improvement of the calculated Green function.
PACS:71.10.Fd, 71.15.-m, 71.27.+a
Поступила в редакцию: 13.09.2007 Исправленный вариант: 18.10.2007