Magnetic excitations in a bond-centered stripe phase: Spin waves far from the semiclassical limit

Using a spin-only model, we compute spin excitation spectra in a bond-centered stripe state with long-range magnetic order. We employ a bond operator formalism, which naturally captures both dimerization and broken spin symmetry in a unified framework. At low energies, the spin excitations resemble spin waves, but at higher energies they are very similar to spin-one excitations of isolated spin ladders. Our theory does well describe neutron scattering data [J. M. Tranquada et al., Nature (London) 429, 534 (2004)] on La2-xBaxCuO4, pointing towards bond order in this material.