Regensburg 2007 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 2: Quantum-Critical Phenomena
TT 2.6: Vortrag
Montag, 26. März 2007, 10:45–11:00, H19
Quantum phase transitions and dimensional reduction in antiferromagnets with inter-layer frustration — •Oliver Rösch, Inga Fischer, and Matthias Vojta — Institut für Theoretische Physik, Universität zu Köln
We discuss phase transitions of quasi-two-dimensional antiferromagnets with a fully frustrated inter-layer interaction. Using symmetry arguments in a perturbation expansion for the order parameter theory and applying the bond-operator method beyond the harmonic approximation, we calculate the magnetic excitation spectrum in different parameter regimes. We consider various crossovers in the vicinity of the quantum critical points and the finite-temperature transitions. We also discuss the relation of our results to recent experiments on BaCuSi2O6 which indicated the possibilty of dimensional reduction through geometric frustration.