Abstract
The magnetization process of S=1/2 XXZ chain, exposed to a periodic field, have been studied with use of density matrix renormalization group (DMRG) method and Jordan-Wigner fermion mean field approximation. In this study, the DMRG calculation has been performed mainly in case of periodic field with a period four times the lattice spacing. The magnetization curves for various values of Ising anisotropy Δ and amplitude of periodic field λ are obtained, exhibiting a plateau for a suitable set of values of Δ and λ. A phase diagram on the plane of Δ and the uniform field h, or on the plane of Δ and λ, has been constructed to show the condition for the `plateau phase' to appear. These results are well interpreted in terms of the renormalized energy band of JW-fermions, moving in a self-consistent periodic field.
