INVESTIGADORES
CABRA Daniel Carlos
artículos
Título:
Bond-impurity induced bound states in disordered spin-1/2 spin ladders
Autor/es:
M. ARLEGO, W. BRENIG, D.C. CABRA, F. HEIDRICH-MEISNER, A. HONECKER, G. ROSSINI
Revista:
PHYSICAL REVIEW B
Editorial:
AMER PHYSICAL SOC
Referencias:
Año: 2004 vol. 70 p. 14436 - 14445
ISSN:
1098-0121
Resumen:
We discuss the effect of weak bond-disorder in two-leg spin ladders on
the
dispersion relation of the elementary triplet excitations with a
particular
focus on the appearance of bound states in the spin gap. Both the cases
of
modified exchange couplings on the rungs and the legs of the ladder are
analyzed. Based on a projection on the single-triplet subspace, the
single-impurity and small cluster problems are treated analytically in
the
strong-coupling limit. Numerically, we study the problem of a single
impurity
in a spin ladder by exact diagonalization to obtain the low-lying
excitations.
At finite concentrations and to leading order in the inter-rung
coupling, we
compare the spectra obtained from numerical diagonalization of large
systems
within the single-triplet subspace with the results of diagrammatic
techniques,
namely low-concentration and coherent-potential approximations. The
contribution of small impurity clusters to the density of states is also
discussed.