Filters

2013 - 20162

More filters

20192
Reset filters

Settings

Subject: Applied mathematics × WGL Institute: IFWD ×

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Heavy fermion properties of the Kondo Lattice model
    (London : Nature Publishing Group, 2013) Sykora, Steffen; Becker, Klaus W.
    We study the S = 1/2 Kondo lattice model which is widely used to describe heavy fermion behavior. In conventional treatments of the model the Kondo interaction is decoupled in favour of a hybridization of conduction and localized f electrons. However, such an approximation breaks the local gauge symmetry and implicates that the local f-occupation is no longer conserved. To avoid these problems, we use in this work an alternative approach to the model based on the Projective Renormalization Method (PRM). Thereby, within the conduction electron spectral function we identify the lattice Kondo resonance as an almost flat excitation near the Fermi surface which is composed of conduction electron creation operators combined with localized spin fluctuations. This leads to an alternative description of the Kondo resonance without having to resort to an artificial symmetry breaking.
  • Thumbnail Image
    Item
    Unconventional superconductivity and interaction induced Fermi surface reconstruction in the two-dimensional Edwards model
    (London : Nature Publishing Group, 2016) Cho, Dai-Ning; van den Brink, Jeroen; Fehske, Holger; Becker, Klaus W.; Sykora, Steffen
    We study the competition between unconventional superconducting pairing and charge density wave (CDW) formation for the two-dimensional Edwards Hamiltonian at half filling, a very general two-dimensional transport model in which fermionic charge carriers couple to a correlated background medium. Using the projective renormalization method we find that a strong renormalization of the original fermionic band causes a new hole-like Fermi surface to emerge near the center of the Brillouin zone, before it eventually gives rise to the formation of a charge density wave. On the new, disconnected parts of the Fermi surface superconductivity is induced with a sign-changing order parameter. We discuss these findings in the light of recent experiments on iron-based oxypnictide superconductors.