Doping-dependent Magnetization Plateaux in P-merized Hubbard Chains * Typeset Using Revt E X * Work Done under Partial Support of the Ec Tmr Programme Integrability, Non-perturbative Effects and Symmetry in Quantum Field Theories

We study zero-temperature Hubbard chains with periodically modulated hopping at arbitrary filling n and magnetization m. We show that the magnetization curves have plateaux at certain values of m which depend on the periodicity p and the filling. At commensurate filling n a charge gap opens and then magnetization plateaux correspond to fully gapped situations. However, plateaux also arise in the magnetization curves at fixed n between the commensurate values and then the plateau-value of m depends continuously on n and can thus also become irrational. In particular for the case of dimerized hopping (p = 2) and fixed doping we find that a plateau appears at m = 1 − n. In this case, there is still a gapless mode on the plateau leading to thermodynamic behavior which is different from a completely gapped situation.