Regensburg 2013 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 25: Correlated Electrons: Low-Dimensional Systems - Models 3
TT 25.3: Vortrag
Dienstag, 12. März 2013, 10:00–10:15, H9
Breakdown of flat bands in highly-frustrated spin systems — •Michael Powalski1, Kris Coester1, Roderich Moessner2, and Kai Phillip Schmidt1 — 1Lehrstuhl für Theoretische Physik I, TU Dortmund, Germany — 2Max Planck Institute for the Physics of Complex Systems, 01187 Dresden, Germany
In several highly-frustrated spin systems the low-energy excitation band is known to be exactly flat up to a certain perturbative order. One important example is the fully-frustrated transverse field Ising model on the kagome lattice. Its lowest one-particle band is extremely flat becoming dispersive only in order eight perturbation theory in the high-field limit. This behaviour can be traced back to the existence of a local mode being an exact eigenstate up to seventh order.
Here we use high-order series expansions to investigate the occurrence and the breakdown of flat bands in geometrically frustrated systems. It is shown that the breakdown of such flat bands is connected to quantum fluctuations which do not interfere destructively. This can be understood intuitively via the used linked cluster expansion.