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Dresden 2017 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 50: Correlated Electrons: Frustrated Magnets - Low-Dimensional Systems

TT 50.2: Talk

Wednesday, March 22, 2017, 15:15–15:30, HSZ 304

Effective spin-Hamiltonian for the 1D Hubbard model at arbitrary coupling strengthRolf Schumann1 and •Stefan-Ludwig Drechsler21Institut 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 J1J2J3, 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[2] S.A. Hamerla and G. Uhrig, unpublished.

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