Regensburg 2007 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 33: Low-dimensional Systems - Models II

TT 33.9: Talk

Friday, March 30, 2007, 12:30–12:45, H18

Confinement of spinons in the spiral staircase model — •Christian Brünger and Fakher Assaad — Universität Würzburg, Germany

We consider two antiferromagnetic spin 1/2 chains with coupling constants J and Jcos²(θ/2) coupled ferromagnetically, J_⊥. In the limit J_⊥→∞ the model maps onto the Haldane spin 1 chain irrespective of te choice of the angle θ. The question we address here is the confinement of spinons in the weak coupling region. As expected from bosonization [1] at θ = 0 the spin gap varies linearly with J_⊥. On the other hand in the limit θ = π our results suggest that this spin gap opens as (J_⊥)^α with α≃ 2. This statement follows from mean-field, exact diagonalization as well as large scale quantum Monte Carlo simulations.

[1] D. G. Shelton, A. A. Nersesyan and A.M. Tsvelik, Phys. Rev. B 53, 8521 (1996)