Magnetic Phase Diagram of the S=1⁄2 Antiferromagnetic Zigzag Spin Chain in the Strongly Frustrated Region: Cusp and Plateau

Abstract

We determine the magnetic phase diagram of the S=1⁄2 antiferromagnetic zigzag spin chain in the strongly frustrated region, using the density matrix renormalization group method. We find the magnetization plateau at 1⁄3 of the full moment accompanying the spontaneous symmetry breaking of the translation, the cusp singularities above and/or below the plateau, and the even–odd effect in the magnetization curve. We also discuss the formation mechanisms of the plateau and cusps briefly.