Middle-Field Cusp Singularities in the Magnetization Process of One-Dimensional Quantum Antiferromagnets

TL;DR

This paper investigates the magnetization process in one-dimensional quantum antiferromagnets, revealing cusp singularities in the magnetization curve linked to energy dispersion features and phase transitions.

Contribution

It introduces a density-matrix renormalization group approach to identify and explain cusp singularities in the magnetization curves of specific quantum antiferromagnets.

Findings

Cusp singularities are observed in the M-H curve of studied models.

Cusp formation correlates with Fermi-liquid to non-Fermi-liquid transition.

Energy dispersion analysis explains the origin of cusp singularities.

Abstract

We study the zero-temperature magnetization process (M-H curve) of one-dimensional quantum antiferromagnets using a variant of the density-matrix renormalization group method. For both the S=1/2 zig-zag spin ladder and the S=1 bilinear-biquadratic chain, we find clear cusp-type singularities in the middle-field region of the M-H curve. These singularities are successfully explained in terms of the double-minimum shape of the energy dispersion of the low-lying excitations. For the S=1/2 zig-zag spin ladder, we find that the cusp formation accompanies the Fermi-liquid to non-Fermi-liquid transition.