Eur. Phys. J. B 38, 535-539 (2004)
https://doi.org/10.1140/epjb/e2004-00149-2

Magnetization plateau and quantum phase transitions in a spin-orbital model

¹ Department of Physics, Hangzhou Teachers College, Hangzhou 310012, P.R. China
² Instituto de Física da UFRGS, Av. Bento Gonçalves 9500, Porto Alegre 91501-970, Brazil
³ Centro Brasileiro de Pesquisas Físicas, Rua Dr. Xavier Sigaud 150, 22290-180 Rio de Janeiro, RJ, Brazil
⁴ Department of Theoretical Physics, Research School of Physical Sciences and Engineering, and Centre for Mathematics and its Applications, Mathematical Sciences Institute, Australian National University, Canberra ACT 0200, Australia

Corresponding author: ^a ying@cbpf.br

Received: 28 October 2003
Revised: 8 January 2004
Published online: 8 June 2004

Abstract

A spin-orbital chain with different Landé g factors and one-ion anisotropy is studied in the context of the thermodynamical Bethe ansatz. It is found that there exists a magnetization plateau resulting from the different Landé g factors. Detailed phase diagram in the presence of an external magnetic field is presented both numerically and analytically. For some values of the anisotropy, the four-component system undergoes five consecutive quantum phase transitions when the magnetic field varies. We also study the magnetization in various cases, especially its behaviors in the vicinity of the critical points. For the SU(4) spin-orbital model, explicit analytical expressions for the critical fields are derived, with excellent accuracy compared with numerics.