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TT: Fachverband Tiefe Temperaturen

TT 14: Spin Systems and Itinerant Magnets

TT 14.7: Vortrag

Dienstag, 27. März 2007, 16:00–16:15, H19

Strongly correlated fermions on frustrated lattices — •Frank Pollmann¹, Kirill Shtengel², Peter Fulde¹, and Erich Runge³ — ¹Max–Planck–Institut für Physik komplexer Systeme, Nöthnitzer Str. 38, 01187 Dresden, Germany — ²Department of Physics, University of California, Riverside, CA 92521, USA — ³Technische Universität Ilmenau, Institut für Physik, 98684 Ilmenau, Germany

Systems with frustrated interactions are generally characterized by a high density of low–lying excitations which leads to a high susceptibility and thus interesting physical effects. The study of frustrated spin systems has revealed numerous fascinating properties, e.g., the realization of liquid phases and an enhanced magnecaloric effect. We focus on charge degrees of freedom on geometrically frustrated lattices. In particular, we study a novel class of strongly correlated fermions which could allow for a possibility of fractionally charged excitations. For a model of strongly correlated spinless fermions on a planar pyrochlore (checkerboard) lattice it has been shown that fractional charges are linearly confined. We consider now a model of spinful fermions on a geometrically frustrated kagome lattice at particular filling factors. Of special interest is again the strongly correlated limit where excitations which carry a fractional charge are possible. An effective Hamiltonian is derived which describes the low–lying excitations. We study the interplay between charge– and spin–degrees of freedom by means of exact diagonalization. In particular we show that the ground state is charge and spin ordered.