Progress of Theoretical Physics Supplement
Cusp Singularity in the Magnetization Curve of 1D Quantum Spin Systems
Kouichi Okunishi
Abstract
We give a short review of the cusp singularity in the magnetization curve of 1D quantum spin systems. We show that the cusp singularity appears for a certain class of nonintegrable frustrated spin systems, using the density matrix renormaziation group method. We also discuss the cusp appearance mechanism on the basis of the one particle dispersion curve of the elementary excitation, where the shape change of the dispersion curve induced by the frustrated interaction plays an essential role.