Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

DY: Dynamik und Statistische Physik

DY 11: Poster I

DY 11.14: Poster

Dienstag, 18. März 1997, 14:30–17:30, F

η-Exponenten im eindimensionalen antiferromagnetischen Heisenbergmodell mit übernächster Nachbarkopplung — •C. Gerhardt¹, A. Fledderjohann¹, E. Aysal¹, K.-H. Mütter¹, J.F. Audet², and H. Kröger² — ¹Fachbereich Physik, Bergische Universität Wuppertal, Gaußstr. 20, D-42097 Wuppertal — ²Department of Physics, Université Laval, Quebec, Canada

We investigate the critical exponents η₃(α,M), η₁(α,M) associated with the singularities in the longitudinal and transverse structure factors of the one dimensional antiferromagnetic Heisenberg model with nearest (J₁) and next to nearest (J₂) neighbour coupling of relative strength α=J₂/J₁ and an external field B with magnetization M(B), using different methods of exact diagonalization. The quantum numbers of the groundstate and the first excited states are obtained, indicating levelcrossings due to the next nearest neighbour coupling. Softmodes in the excitation spectrum are studied and the associated quantities θ₁ and θ₃ are calculated. A simple relation between the η exponents and the quantities θ – predicted by conformal field theory – is shown to hold in a large region of the coupling constant α.