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arXiv:cond-mat/9808345 · Physical review. B, Condensed matter

Magnon wave function and impurity effects in S=1 antiferromagnetic chains: A large- n approach

Alistair Savage, Ian K. Affleck

Published Feb 1, 1999• 1 citation
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Abstract

A large-$n$ approximation to the $S=1$ antiferromagnetic chain, using the symmetric tensor representation and its conjugate, is developed to order $1/n$ in order to calculate the magnon wave function and to study the effect of modifying the exchange coupling from J to ${J}^{\ensuremath{'}}$ on a single link. It is shown that a magnon bound state exists below the Haldane gap for arbitrarily small negative ${J}^{\ensuremath{'}}\ensuremath{-}J$ but only above a certain critical value of ${J}^{\ensuremath{'}}\ensuremath{-}J$ for positive values. In the former case the binding energy vanishes as $(J\ensuremath{-}{J}^{\ensuremath{'}}{)}^{2}.$

DOI
10.1103/physrevb.59.3635

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A large-nnn approximation to the S=1S=1S=1 antiferromagnetic chain, using the symmetric tensor representation and its conjugate, is developed to order 1/n1/n1/n in order to calculate the magnon wave function and to study the effect of modifying the exchange coupling from J to J\ensuremath′{J}^{\ensuremath{'}}J\ensuremath′ on a single link. It is shown that a magnon bound state exists below the Haldane gap for arbitrarily small negative J\ensuremath′\ensuremath−J{J}^{\ensuremath{'}}\ensuremath{-}JJ\ensuremath′\ensuremath−J but only above a certain critical value of J\ensuremath′\ensuremath−J{J}^{\ensuremath{'}}\ensuremath{-}JJ\ensuremath′\ensuremath−J for positive values. In the former case the binding energy vanishes as (J\ensuremath−J\ensuremath′)2.(J\ensuremath{-}{J}^{\ensuremath{'}}{)}^{2}.(J\ensuremath−J\ensuremath′)2.
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