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TT: Fachverband Tiefe Temperaturen

TT 20: Correlated Electrons - Poster Session

TT 20.68: Poster

Mittwoch, 28. März 2007, 14:00–17:45, Poster A

From antiferromagnetism to singlet phase in the Double Bethe lattice — •Hartmut Hafermann¹, Mikhail Katsnelson², and Alexander Lichtenstein¹ — ¹I. Institute für Theoretische Physik, Universität Hamburg, D-20355 Hamburg — ²Institute for Molecules and Materials, Radboud University Nijmegen, 6525 ED Nijmegen, The Netherlands

We consider a model of two coupled Bethe lattices with hopping t on each sublattice, perpendicular hopping t_⊥ between the lattices and an on-site repulsion U. We studied the magnetic phase transition from the antiferromagnetic to the non-magnetic state as a function of perpendicular hopping within the Continuous-Time Quantum Monte Carlo approach. For sufficiently large values of U, the transition is found to occur at t_⊥/t=√2. By measuring the total spin, it is shown that the non-magnetic state is a singlet state. We further map out the t_⊥-U-phase diagram.