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TT: Fachverband Tiefe Temperaturen

TT 32: Correlated Electrons: Poster Session

TT 32.70: Poster

Thursday, February 28, 2008, 14:00–18:00, Poster B

Does There Exist a Baym-Kadanoff Construction for the Heisenberg Model? — •Stephan Filor and Thomas Pruschke — Institut für Theoretische Physik, Georg-August-Universität Göttingen

A powerful tool for treating fermionic systems in a cluster approximation is the self-energy functional approach developed by Potthoff [1]. Our goal is to generalize this idea to the general (anisotropic) Spin-Heisenberg model.

To that end an analogue of a Baym-Kadanoff construction for the free energy as a functional of dynamical quantities such as green functions respectively self-energies is needed. Due to the structure of the spin operator algebra, which differs essentially from the usual one for fermions or bosons, this is not possible to achieve in a straightforward way.

To solve the problem we resort to the spin diagram technique proposed by Izyumov et. al. [2] which we use to develop a suitable variational approach to a Heisenberg lattice.

[1] M. Potthoff, Eur. Phys. J. B 32, 429 (2003)

[2] Y.A. Izyumov, Y.N. Skryabin, Statistical Mechanics of Magnetically Ordered Systems, Plenum, New York (1988)