Regensburg 2007 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 24: Symposium “Condensed Matter Phases in Ultracold Atoms”
TT 24.5: Talk
Thursday, March 29, 2007, 11:35–12:00, H20
Multicolor Hubbard models with ultracold atoms — •Carsten Honerkamp — Universität Würzburg, Am Hubland, D-97074 Würzburg
In ultracold atomic systems, the hyperfine states provide an internal degree of freedom which may allow for the realization of novel many-particle states without obvious ancestors in solid state physics. Here we review our results (most recent: A. Rapp, G. Zarand, C. Honerkamp, W. Hofstetter, cond-mat/0607138) on fermionic SU(N)-Hubbard models on optical lattices where N denotes the number of hyperfine states (colors) loaded into the lattice. In the case of repulsive interactions on the half-filled square lattice, staggered current phases replace generalized antiferromagnetic ordering above a critical color number. For the attractive case we focus on N=3, as this can be possibly realized using 6Li. For weak attractions and generic densities, the variational ground-state is a color-superfluid with an ungapped branch of single-particle excitations. For increasing attraction, an extended variational ansatz reveals a continuous quantum phase transition toward a color-confining heavy-fermion phase with bound states of three particles, mimicking the QCD phase transition a high matter density. For low densities in our lattice model, this transition can be interpreted in simple two-fluid model.