Dresden 2017 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
TT: Fachverband Tiefe Temperaturen
TT 50: Correlated Electrons: Frustrated Magnets - Low-Dimensional Systems
TT 50.2: Vortrag
Mittwoch, 22. März 2017, 15:15–15:30, HSZ 304
Effective spin-Hamiltonian for the 1D Hubbard model at arbitrary coupling strength — Rolf Schumann1 and •Stefan-Ludwig Drechsler2 — 1Institut für Theoretische Physik, TU Dresden, D-01062,Germany — 2Institute for Solid State Theory, Leibniz-Instiitute IFW-Dresden, D-01171 Dresden. Germany
Using exact diagonalization analytical results for small clusters (dimers, trimers and tetramers) we derive an approximate effective spin-Hamiltonian valid for any ratio u=U/t, where U denotes the on-site Coulomb repulsion and t is the nearest neighbor (NN)-transfer integral. Thereby we present analytical results for the first, second (NNN), third neighbor exchange integrals J1 ≫ J2 ≫ J3, respectively, and also for the leading cyclic quartic (four spin) exchange term. All interaction parameters are smooth monotonous functions of u without any artificial divergency at u=4 or even u=0 as in other methods based on perturbational theory. Our results compare well with those for the NN (analytical expression) and the NNN (numerical data are available in the limit u ≥ 4, only) exchange integrals J1 and J2, respectively, obtained within the flow-equation technique [1,2]. Possible applications for "conducting" polymers and spin-Peierls systems being in the intermediate coupling regime are briefly disussed.
[1] S.A. Hamerla et al., Phys. Rev. B 82, 235117 (2010)
[2] S.A. Hamerla and G. Uhrig, unpublished.