Fractional and integer excitations in quantum antiferromagnetic spin 1/2 ladders - art. no. 167204

Spectral densities are computed in unprecedented detail for quantum anti fe rromagnetic spin 1/2 two-leg ladders. These results were obtained due to a major methodical advance achieved by optimally chosen unitary transformatio ns. The approach is based on dressed integer excitations. Considerable weig ht is found at high energies in the two-particle sector. Precursors of frac tional spinon physics occur supporting the conclusion that there is no nece ssity to resort to fractional excitations in order to describe features at higher energies.