Evidence for composite nature of quasiparticles in the 2D t-J model

It is shown that the dynamics of a single hole in a quantum antiferromagnet (described by the t--J model) can be simply understood in terms of a composite quasiparticle. This description provides naturally two different energy scales t and J corresponding to the inverse masses of the charge (holon) and spin (spinon) elementary excitations respectively. This picture is consistent with the exact results obtained on small clusters for the single hole spectral function and optical conductivity providing that one assumes the existence of a string-like force of magnitude J between the holon and the spinon. Then the hole quasiparticle can be interpreted as a bound state of its two constituents.