Regensburg 2013 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 7: Correlated Electrons: Spin Systems, Itinerant Magnets 1
TT 7.8: Vortrag
Montag, 11. März 2013, 11:30–11:45, H19
Strongly Correlated Fermions on a Kagome Lattice: Interplay between Spin and Charge Degrees of Freedom — •Krishanu Roychowdhury1, Karlo Penc2, Chisa Hotta3, and Frank Pollmann1 — 1Max-Planck-Institute fur Physik of Komplexer Systeme, 01187 Dresden, Germany — 2Research Institute for Solid State Physics and Optics, H-1525 Budapest, P.O.B. 49, Hungary — 3Department of Physics, Faculty of Science, Kyoto Sangyo University, Kyoto 603-8555, Japan
We study strongly correlated electrons on a kagome lattice at 1/3 filling (i.e. two electrons per three sites). The dynamics is described by an extended Hubbard Hamiltonian. We are concerned with the limit |t|<<V<<U with hopping amplitude t, nearest-neighbour repulsion V and on-site repulsion U. In this limit, we can neglect double occupancy on the sites as well as states with more than two electrons per triangle. The low energy physics is described by an effective Hamiltonian which includes ring exchange of fermions around hexagons with amplitude g as well as an antiferromagnetic Heisenberg interaction with amplitude J. Using large scale exact-diagonalization, we observe a quantum-phase transition from a resonating plaquette phase at large g/J to a charge ordered phase at low values of g/J. To study the finite temperature physics, we consider a classical version of the problem in which we investigate the effects of a loop tension. This loop tension results from the spin-fluctuations and favours configurations with short loops.