Dresden 2006 – scientific programme
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TT: Tiefe Temperaturen
TT 12: Correlated Electrons: Low-dimensional Systems - Models
TT 12.1: Talk
Tuesday, March 28, 2006, 09:30–09:45, HSZ 304
Entropy of fermionic models on highly frustrated lattices — •Andreas Honecker1 and Johannes Richter2 — 1Technische Universität Braunschweig, Mendelssohnstrasse 3, 38106 Braunschweig, Germany — 2Institut für Theoretische Physik, Otto-von-Guericke Universität Magdeburg, 39016 Magdeburg, Germany
Fermionic models and quantum antiferromagnets at high magnetic fields on highly frustrated lattices are characterized by a lowest single-particle band which is completely flat. On the one hand, this is known to give rise to flat-band ferromagnetism for the repulsive Hubbard model on such lattices. On the other hand, exact ground states consisting of localized magnons have recently been constructed and studied for the quantum Heisenberg antiferromagnet on the same lattices. Here we combine both aspects and discuss the entropy and ground state degeneracy on such lattices. Spinless fermions not only provide a simple soluble example, but also give rise to a class of ground states of the repulsive Hubbard model. The sawtooth chain is discussed in particular detail.