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Article Dans Une Revue Physical Review Letters Année : 2008

Spin gap and string order parameter in the ferromagnetic Spiral Staircase Heisenberg Ladder: a quantum Monte Carlo study

C. Brünger
  • Fonction : Auteur
F. F. Assaad
  • Fonction : Auteur
D. N. Aristov
  • Fonction : Auteur
M. N. Kiselev
  • Fonction : Auteur

Résumé

We consider a spin-1/2 ladder with a ferromagnetic rung coupling J_\perp and inequivalent chains. This model is obtained by a twist (\theta) deformation of the ladder and interpolates between the isotropic ladder (\theta=0) and the SU(2) ferromagnetic Kondo necklace model (\theta=\pi). We show that the ground state in the (\theta,J_\perp) plane has a finite string order parameter characterising the Haldane phase. Twisting the chain introduces a new energy scale, which we interpret in terms of a Suhl-Nakamura interaction. As a consequence we observe a crossover in the scaling of the spin gap at weak coupling from \Delta/J_\| \propto J_\perp/J_\| for \theta < \theta_c \simeq 8\pi/9 to \Delta/J_\| \propto (J_\perp/J_\|)^2 for \theta > \theta_c. Those results are obtained on the basis of large scale Quantum Monte Carlo calculations.

Dates et versions

hal-00169456 , version 1 (04-09-2007)

Identifiants

Citer

C. Brünger, F. F. Assaad, Sylvain Capponi, Fabien Alet, D. N. Aristov, et al.. Spin gap and string order parameter in the ferromagnetic Spiral Staircase Heisenberg Ladder: a quantum Monte Carlo study. Physical Review Letters, 2008, 100 (1), pp.017202. ⟨10.1103/PhysRevLett.100.017202⟩. ⟨hal-00169456⟩
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