Confinement-deconfinement transition and spin correlations in a generalized Kitaev model

Mandal, S. ; Bhattacharjee, Subhro ; Sengupta, K. ; Shankar, R. ; Baskaran, G. (2011) Confinement-deconfinement transition and spin correlations in a generalized Kitaev model Physical Review B: Condensed Matter and Materials Physics, 84 (15). 155121_1-155121_9. ISSN 1098-0121

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Official URL: http://prb.aps.org/abstract/PRB/v84/i15/e155121

Related URL: http://dx.doi.org/10.1103/PhysRevB.84.155121

Abstract

We present a spin model, namely, the Kitaev model augmented by a loop term and perturbed by an Ising Hamiltonian, and show that it exhibits both confinement-deconfinement transitions from spin liquid to antiferromagnetic/spin-chain/ferromagnetic phases and topological quantum phase transitions between gapped and gapless spin-liquid phases. We develop a fermionic resonating-valence-bonds (RVB) mean-field theory to chart out the phase diagram of the model and estimate the stability of its spin-liquid phases, which might be relevant for attempts to realize the model in optical lattices and other spin systems. We present an analytical mean-field theory to study the confinement-deconfinement transition for large coefficient of the loop term and show that this transition is first order within such mean-field analysis in this limit. We also conjecture that in some other regimes, the confinement-deconfinement transitions in the model, predicted to be first order within the mean-field theory, may become second order via a defect condensation mechanism. Finally, we present a general classification of the perturbations to the Kitaev model on the basis of their effect on it's spin correlation functions and derive a necessary and sufficient condition, within the regime of validity of perturbation theory, for the spin correlators to exhibit a long-ranged power-law behavior in the presence of such perturbations. Our results reproduce those of Tikhonov et al. [ Phys. Rev. Lett. 106 067203 (2011)] as a special case.

Item Type:Article
Source:Copyright of this article belongs to The American Physical Society.
ID Code:81682
Deposited On:07 Feb 2012 06:16
Last Modified:13 Jul 2012 11:40

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