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TT: Fachverband Tiefe Temperaturen

TT 15: Correlated Electrons: Metal-Insulator Transition 2

TT 15.11: Vortrag

Dienstag, 24. März 2009, 12:30–12:45, HSZ 301

Magnetic field induced semimetal-to-canted-anti-ferromagnet transition on the honeycomb lattice — •Martin Bercx and Fakher Assaad — TP1, Universität Würzburg

It is shown that the semi-metallic state with point like Fermi surface of the two-dimensional honeycomb lattice is unstable towards a canted anti-ferromagnetic insulator upon application of an in-plane magnetic field. This instability is already present at the mean-field level; the magnetic field shifts in opposite directions the up and down spin cones thereby generating a finite density of states at the Fermi surface and perfect nesting between the up and down Fermi sheets. This prefect nesting triggers a canted anti-ferromagnetic insulating state. Those conclusions, based on mean-field arguments, are confirmed with projective Quantum Monte Carlo methods on lattices up to 12 × 12 unit cells.