Annalen der Physik

Color contour plot of the momentum resolved total spectral function of the iron pnictide compound BaFe₂As₂ near the X and Γ points, respectively, of the Brillouin zone. The results were obtained within the LDA+DMFT approach, a computational scheme for the realistic modelling of correlated electron materials based on the combination of density functional theory in the local density approximation (LDA) with dynamical mean-field theory (DMFT). Picture: After S. L. Skornyakov, A. V. Efremov, N. A. Skorikov, M. A. Korotin, Yu. A. Izyumov, V. I. Anisimov, A. V. Kozhevnikov, and D. Vollhardt; Phys. Rev. B 80, 092501 (2009)

In this paper basic terms of the physics of correlated electrons are explained. In particular, some of the steps that led to the formulation of a comprehensive non-perturbative many-body approach to correlated quantum many-body systems – the dynamical mean-field theory (DMFT) – are described.

Through the motivation of the recent discovery of dispersionless regions in the band structure of the delafossites, a model density of states of free fermions including a d anomaly is studied. The resulting temperature dependence of the chemical potential is obtained both exactly and by different approximation schemes which are then discussed thoroughly.

Ferromagnet/Superconductor/Ferromagnet (F/S/F) trilayers, in which the establishing of a Fulde-Ferrell Larkin-Ovchinnikov (FFLO) like state leads to interference effects of the superconducting pairing wave function, form the core of the superconducting spin valve. The realization of strong critical temperature oscillations in such trilayers, as a function of the ferromagnetic layer thicknesses, are the key condition to obtain a large shift in the critical temperature.

A generalization of the recently developed dual-fermion approach introduced for correlated lattices to non-equilibrium problems is presented. In its local limit, the approach has been used to devise an efficient impurity solver, the superperturbation solver for the Anderson impurity model (AIM). It is shown that the general dual perturbation theory can be formulated on the Keldysh contour.

Mach provided an operational definition for inertial mass and pointed out that time and space are conceptually distinct from their operational definitions by means of masses. Mach recognized that this circumstance is due to the lack of any a priori connection between the inertial mass of a body and its Newtonian state in space and time. One possible way to improve upon this situation in classical physics is to associate mass with an extra dimension.