Interplay of holon and spinon dynamics in doped anisotropic Heisenberg chains

The role played by doping in one-dimensional quantum antiferromagnets is investigated using a decoupling of the charge and spin degrees of freedom that allows for magnetic phase changes when the concentration of holes increases. Our approach predicts quasi-continuous as well as discontinuous metal-insulator transitions, depending on the nature of the corresponding magnetic transformation. We also provide a clue for the observed behavior of the Hall coefficient, with a sign change caused by doping, suggesting that the change in the character of carriers is related to different magnetic correlations.