Fakultät für Physik und Astronomie

    SFB Colloquium

    "Green's functions for the theoretical description of strongly correlated electrons systems"
    Datum: 12.12.2019, 16:15 - 18:00 Uhr
    Kategorie: Kolloquium
    Ort: Hubland Süd, Geb. P1 (Physik), HS P
    Veranstalter: SFB 1170 ToCoTronics
    Vortragende*r: Dr. Georg Rohringer - University of Hamburg
    Green's functions represent one of the most useful tools for the theoretical description of correlated lattice electrons. In particular, 
    the one-particle Green's function contains information about the spectral properties of the system and can be directly compared to 
    (angular resolved) photoemission spectroscopy experiments. However, also two-particle correlation functions provide very interesting 
    insights into the properties of correlated electron systems as they contain crucial information on response functions such as the 
    magnetic susceptibility or the optical conductivity. In my talk, I will present an overview about the physical content as well as the 
    applications of one- and two-particle Green's and vertex functions in frontier condensed matter research. First, I will demonstrate how 
    the inclusion of local correlation effects into the one-particle Green's function by means of dynamical mean field theory (DMFT) can 
    lead to a breakdown of the topological quantization of the Hall conductivity in the Hubbard model in a magnetic field. The limitations 
    of the purely local description of DMFT leads me to the discussion how local frequency-dependent vertices can be used to include 
    also non-local correlations effects in interacting many-electron systems beyond DMFT. While these so-called diagrammatic extensions[1] 
    of DMFT have been successfully exploited to describe collective phenomena such as magnetism and superconductivity, their predictive 
    power is still limited by specific inconsistencies between the one- and the two-particle level[2]. In the final part of my talk, I will present 
    possible solutions to these problems[3] which I will address in the framework of my Emmy Noether project at the university of Hamburg.
    [1] G. Rohringer et al., Rev. Mod. Phys. 90, 025003 (2018).
    [2] E. G. C. P. van Loon et al., Phys. Rev. B 93, 155162 (2016).
    [3] G. Rohringer, and A. Toschi, Phys. Rev. B 94, 125144 (2016).