Quantum vs. Classical Magnetization Plateaus of S=1/2 Frustrated Heisenberg Chains

TL;DR

This paper investigates the competition between quantum and classical magnetization plateaus in S=1/2 frustrated Heisenberg chains, analyzing their stability, phase transitions, and the underlying models using various theoretical and numerical methods.

Contribution

It introduces a detailed analysis of the stability and transition between quantum and classical plateau states in frustrated chains, including new models with exact quantum plateau states.

Findings

Classical udu-type plateau at 1/3 saturation is stabilized by exchange modulation.

Quantum 00u-type plateau state is favored by period 3 exchange modulation.

Phase diagram reveals transitions between classical and quantum plateau states.

Abstract

The competition between quantum and classical magnetization plateaus of S=1/2 frustrated Heisenberg chains with modified exchange couplings is investigated. The conventional S=1/2 frustrated Heisenberg chains is known to exhibit a 3-fold degenerate udu-type classical plateau at 1/3 of the saturation magnetization accompanied by the spontaneous Z_3 translational symmetry breakdown. The stability of this plateau phase against period 3 exchange modulation which favors the 00u-type quantum plateau state (00= singlet dimer) is studied by bosonization, renormalization group and numerical diagonalization methods. The ground state phase diagram and the spin configuration in each phase are numerically determined. The translationally invariant Valence Bond Solid-type model with 4-spin and third neighbor interactions, which has the exact 00u-type quantum plateau state, is also presented. The phase transition to the classical udu-type ground state is also observed by varying the strength of 4-spin and third neighbor interactions. The relation between these two types of models with quantum plateau states is discussed.