Journal of the Physical Society of Japan
High-Field Phase Transitions in Integrable Quantum Spin Chains
Hirohito Kiwata, Yasuhiro Akutsu
Abstract
We study the integrable SU( M ) and SU q ( M ) quantum spin chains in the high-magnetic-field region at zero temperature. For M =4 we found second-order phase transitions at two different fields, H 1 and H 2 . At both transition points, the magnetization curve versus magnetic field has cusps with discontinuities in the magnetic susceptibility. We clarify the mechanism of the phase transitions, from which we conclude that the SU( M ) and S U q ( M ) quantum spin chains undergo ( M -2) times field-induced phase transitions at zero temperature.