Incommensurate structure of a spin density wave in the one-dimensional t-Jmodel

We make use of the slave-boson approach to investigate the magnetic propert ies of the one-dimensional I - J model in the weak-coupling limit J < t(1 - n), where n is the number of electrons per unit cell. In the mean-field ap proximation at zero temperature we find that the helix spin-density-wave ph ase has a lower energy than the Neel phase. This latter disappears below a critical electron density n(c), whereas the helix phase persists for all ra , The hole-doping dependence of the spin-density-wave amplitude Delta and o f the helix wave-vector q(0) are calculated. The temperature vs hole doping phase diagram in the mean-field approximation is also determined. It is sh own that for n above a certain value n* the helix state transforms into the Neel stare by increasing the temperature as q(0) is reduced to zero. The N eel phase evolves towards the paramagnetic phase at higher temperatures. Fo r n below n* the helix phase transforms directly into the paramagnetic phas e by increasing the temperature. (C) 1999 Elsevier Science B.V. All rights reserved.