Symmetric and asymmetric excitations of a strong-leg quantum spin ladder

The zero-field excitation spectrum of the strong-leg spin ladder (C7H10N)(2)CuBr4 is studied with a neutron time-of-flight technique. The spectrum is decomposed into its symmetric and asymmetric parts with respect to the rung momentum and compared with theoretical results obtained by the density matrix renormalization group method. Additionally, the calculated dynamical correlations are shown for a wide range of rung and leg coupling ratios in order to point out the evolution of arising excitations, as, e.g., of the two-magnon bound state from the strong to the weak coupling limit.