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 La2−xBaxCuO4 had been interpreted previously as evidence for bond-centered stripes. In a recent article, however, we determined the magnetic coupling induced by the charge stripes between bondor site-centered spin stripes modeled by twoor three-leg ladders, respectively. We found that only the site-centered models order, while the coupling in bond-centered models is insufficient to trigger the quantum phase transition into the magnetically ordered state. 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.