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TT: Fachverband Tiefe Temperaturen

TT 24: Correlated Electrons: Low-dimensional Systems - Models

TT 24.10: Talk

Wednesday, February 27, 2008, 16:30–16:45, H 2053

Hybrid approach for quantum antiferromagnets in a uniform magnetic field: Method — •Andreas Kreisel, Francesca Sauli, Nils Hasselmann, and Peter Kopietz — Institut für Theoretische Physik, Universität Frankfurt, Max-von-Laue Straße 1, 60438 Frankfurt, Germany

The properties of ordered quantum antiferromagnets can be calculated by an expansion in inverse powers of the spin quantum number S via the Holstein-Primakoff transformation of the underlying Heisenberg model, or by a renormalization group approach to the non-linear sigma model (NLSM). The relation between these descriptions can be made precise by expressing the canonical magnon operators in the spin-wave approach in terms of hermitian field operators which represent the uniform and staggered components of the spin operators. An effective action for the staggered spin fluctuations (low energy degrees of freedom) has been derived for the case of vanishing magnetic field [1]. We now generalize the approach to quantum antiferromagnets in a uniform magnetic field and discuss the resulting interaction vertices in comparison with those of the NLSM and the conventional 1/S expansion.
 [1] N. Hasselmann and P. Kopietz, Europhys. Lett. 74, 1067 (2006)