Breakdown of a Magnetization Plateau in Ferrimagnetic Mixed Spin-(1/2,S) Heisenberg Chains Due to a Quantum Phase Transition Towards the Luttinger Spin Liquid

TL;DR

This paper investigates how a magnetization plateau in ferrimagnetic mixed spin chains breaks down due to a quantum phase transition to a Luttinger spin liquid, using density-matrix renormalization group calculations.

Contribution

It demonstrates the existence of a single magnetization plateau across various spin values and identifies the quantum phase transition to a Luttinger spin liquid.

Findings

Existence of one magnetization plateau for all studied spins

Breakdown of the plateau at a quantum phase transition

Continuous magnetization change until saturation

Abstract

Magnetization curves of the ferrimagnetic mixed spin-(1/2,S) Heisenberg chains are calculated with the help of density-matrix renormalization group method for several quantum spin numbers S=1, 3/2, 2 and 5/2. It is shown that the ferrimagnetic mixed spin-(1/2,S) Heisenberg chains exhibit irrespective of the spin value S exactly one intermediate magnetization plateau, which can be identified with the gapped Lieb-Mattis ferrimagnetic ground state. The magnetization plateau due to the Lieb-Mattis ferrimagnetism breaks down at a quantum phase transition towards the Luttinger spin liquid, which is characterized by a continuous change of the magnetization with the magnetic field until another quantum critical point is reached at the saturation field.