Magnetic Excitations in the Site-Centered Stripe Phase: Spin Wave Theory of Coupled Three-Leg Ladders

The success of models of coupled two-leg spin ladders in describing the magnetic excitation spectrum of La_{2-x}Ba_xCuO_4 had been interpreted previously as evidence for bond-centered stripes. In a recent article, however, we have determined the magnetic coupling induced by the charge stripes between bond- or site-centered spin stripes modeled by two- or three-leg ladders, respectively. We found that only the site-centered models order. We further indicated excellent agreement of a fully consistent analysis of coupled three-leg ladders using a spin wave theory of bond with the experimental data. Here, we provide a full and detailed account of this analysis.