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TT: Fachverband Tiefe Temperaturen

TT 14: Correlated Electrons: Low-Dimensional Systems - Models 2

TT 14.9: Vortrag

Montag, 11. März 2013, 17:15–17:30, H9

Flat-band ferromagnetic transition on a Bethe lattice — •Mykola Maksymenko¹, Kirill Shtengel², and Roderich Moessner¹ — ¹MPIPKS, 01187 Dresden, Germany — ²Department of Physics and Astronomy, University of California, Riverside, California 92521, USA

An exotic example of itinerant-electron magnetism is the so-called "flat-band ferromagnetism", in a wide class of geometrically frustrated lattices. Here electrons become trapped in restricted parts of the lattice and interactions may favor a ferromagnetic state across a range a electronic fillings.

We provide an exact solution for the problem of the para-ferro transition in a Hubbard model on lattices in which trapping cells form a Bethe lattice. This can be studied as a Pauli-correlated percolation transition in which due to spin-rotational degeneracy, different clusterings of electrons obtain different statistical weights [1]. As in the case of recent numerical studies for the 2D case, we show that the paramagnetic phase persists beyond the uncorrelated percolation point and the transition is via a first-order jump to an unsaturated ferromagnetic phase.
[1] M. Maksymenko, A. Honecker, R. Moessner, J. Richter, and O. Derzhko, Phys. Rev. Lett. 109, 096404 (2012)