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Bound states in weakly disordered spin ladders

M. Arlego·W. Brenig·D. C. Cabra·F. Heidrich-Meisner·A. Honecker·G. Rossini
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Abstract

We study the appearance of bound states in the spin gap of spin-1/2 ladders induced by weak bond disorder. Starting from the strong-coupling limit, i.e., the limit of weakly coupled dimers, we perform a projection on the single-triplet subspace and derive the position of bound states for the single impurity problem of one modified coupling as well as for small impurity clusters. The case of a finite concentration of impurities is treated with the coherent-potential approximation in the strong-coupling limit and compared with numerical results. Furthermore, we analyze the details in the structure of the density of states and relate their origin to the influence of impurity clusters.

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M. Arlego, W. Brenig, D. C. Cabra, F. Heidrich-Meisner, A. Honecker, G. Rossini. 2004-11-30. Bound states in weakly disordered spin ladders. https://doi.org/10.1016/j.physb.2005.01.435

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