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TT: Tiefe Temperaturen

TT 11: Correlated Electrons - Spin Systems and Itinerant Magnets: Theory

TT 11.3: Talk

Saturday, March 5, 2005, 09:15–09:30, TU H2053

Renormalization of spin-wave velocity and frustration in Heisenberg Quantum antiferromagnets — •Frank Krüger and Stefan Scheidl — Institut für Theoretische Physik, Uni Köln

Frustrated quantum antiferromagnets exhibit nontrivial quantum phase transitions which are the subject of extensive current research. We characterize the Néel phase for a two-dimensional Heisenberg model as a function of spin S and the frustration between nearest and next-nearest exchange couplings on a square lattice. We extend the renormalization group approach by Chakravarty, Halperin and Nelson [Phys. Rev. B 39, 2344 (1989)] to account for the discrete lattice structure. As a consequence, we obtain a renormalization of the spin-wave velocity and the frustration strength, which become significant well before the Néel order becomes instable.