Regensburg 2019 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 2: Correlated Electrons: Electronic Structure Calculations and Other Theoretical Topics
TT 2.9: Vortrag
Montag, 1. April 2019, 11:45–12:00, H7
Extended Hubbard Model with nearest neighbor exchange interaction — •Edin Kapetanovic1,2, Malte Schüler1,2, Gerd Czycholl1, and Tim Wehling1,2 — 1Institute for Theoretical Physics, Universtity of Bremen — 2Bremen Center for Computational Materials Science, Universtity of Bremen
We study an extended Hubbard model (EHM) taking into account nearest neighbor direct Coulomb and exchange interactions. Whereas the simple EHM (without exchange interaction) can be mapped on a simple Hubbard model with renormalized on-site interaction Ũ, the EHM with ferromagnetic exchange (i.e. the extended Hubbard-Heisenberg model) at half filling, allows for both, ferro- and antiferromagnetic phases, which is not captured by a simple Hubbard model. For the case of intermediate coupling strengths, which cannot be addressed by perturbation theory or similar approaches, we apply a variational scheme by mapping the EHM with exchange on an effective Hubbard model within an effective magnetic field. In the aforementioned parameter regime we find a partly magnetized phase where the kinetic energy is still significant. In contrast to the known limiting cases, a first order magnetic transition to the fully magnetized state occurs. Further study of these phenomena may provide insight on exotic magnetic phases within correlated materials. For performing the variation we rely on exact numerical solutions of the effective Hubbard model on finite clusters using determinant quantum Monte Carlo.