Interacting magnetic excitations in quantum spin systems - Thermodynamic investigations

PD Dr. Bernd Wolf
Physikalisches Institut, J.W. Goethe-Universität Frankfurt
Tel.: +49-69-798-47243
Fax: +49-69-798-47250
E-mail: wolf@physik.uni-frankfurt.de

Prof. Dr. Michael Lang
Physikalisches Institut, J.W. Goethe-Universität Frankfurt
Tel.: +49-69-798-47241
Fax: +49-69-798-47250
E-mail: michael.lang@physik.uni-frankfurt.de

The project focuses on the collective behaviour of magnetic excitations in quantum-spin systems, including the proposed Bose-Einstein condensation of triplet excitations, under variation of physical and/or chemical parameters. The main objectives will be to search for new phenomena when the bosons are confined to layers or when the bosons' kinetic energy becomes comparable to the potential energy giving rise to a competition between boson localisation and condensation. Special attention will be paid to the effects of the underlying crystal lattice and frustrating interactions.

The materials to be studied here will be synthesised in the projects Aßmus/Ritter (B4) and Wagner/Holthausen/Baumgarten (B5). The experimental results of this project and of the electronic structure determination in Aeschlimann/Felser/Schönhense (B8) will be analysed on the basis of the ab initio calculations in Jeschke/Valentí (B2) and the field theoretical methods in Kopietz (A8) and will be fed back to the syntheses projects to guide the development of new materials. The effects of impurities will be studied theoretically in Eggert (B3).