Cusp Singularities in the Magnetization Curve of Frustrated Kondo Necklace Model

Abstract

Magnetization processes of frustrated Kondo necklace model are studied by means of a density matrix renormalization group (DMRG) method and an elementary band theory based on a bond-operator formalism. The DMRG calculations clearly show the cusp singularity in a low-magnetization region (0<m<1⁄2) besides that in a high-magnetization region (1⁄2<m<1) which is expected from previous studies on the magnetization curve of the Majumdar–Ghosh model. An appearance mechanism of the low-magnetization cusp is interpreted in terms of a double-well shape of a low-energy band arising from frustrations between nearest- and next-nearest-neighbor interactions. We also discuss critical behaviors of magnetization near the cusp and obtain a phase diagram showing whether the cusp appears in the magnetization curve or not.