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Three-Dimensional Ordering in Weakly Coupled Antiferromagnetic Ladders and Chains

Stefan Wessel·Stephan Haas
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Abstract

A theoretical description is presented for low-temperature magnetic-field induced three-dimensional (3D) ordering transitions in strongly anisotropic quantum antiferromagnets, consisting of weakly coupled antiferromagnetic spin-1/2 chains and ladders. First, effective continuum field theories are derived for the one-dimensional subsystems. Then the Luttinger parameters, which determine the low-temperature susceptibilities of the chains and ladders, are calculated from the Bethe ansatz solution for these effective models. The 3D ordering transition line is obtained using a random phase approximation for the weak inter-chain (inter-ladder) coupling. Finally, considering a Ginzburg criterion, the fluctuation corrections to this approach are shown to be small. The nature of the 3D ordered phase resembles a Bose condensate of integer-spin magnons. It is proposed that for systems with higher spin degrees of freedom, e.g. N-leg spin-1/2 ladders, multi-component condensates can occur at high magnetic fields.

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Stefan Wessel, Stephan Haas. 1999-10-18. Three-Dimensional Ordering in Weakly Coupled Antiferromagnetic Ladders and Chains. https://doi.org/10.1103/physrevb.62.316

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