Integrable models and quantum spin ladders: comparison between theory and experiment for the strong coupling ladder compounds

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Publisher: Taylor & Francis Ltd

ISSN: 1460-6976

Source: Advances In Physics, Vol.56, Iss.3, 2007-05, pp. : 465-543

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Abstract

This article considers recent advances in the investigation of the thermal and magnetic properties of integrable spin ladder models and their applicability to the physics of strong coupling ladder compounds. For this class of compounds the rung coupling J⊥ is much stronger than the coupling J∥ along the ladder legs. The ground state properties of the integrable two-leg spin- [image omitted] and the mixed spin-( [image omitted]) ladder models at zero temperature are analysed by means of the Thermodynamic Bethe Ansatz (TBA). Solving the TBA equations yields exact results for the critical fields and critical behaviour. The thermal and magnetic properties of the models are discussed in terms of the recently introduced High Temperature Expansion (HTE) method, which is reviewed in detail. In the strong coupling region the integrable spin- [image omitted] ladder model exhibits three quantum phases: (i) a gapped phase in the regime [image omitted], (ii) a fully polarized phase for [image omitted], and (iii) a Luttinger liquid magnetic phase in the regime Hc1