Frustrated quantum Heisenberg ferrimagnetic chains

TL;DR

This paper investigates the effects of frustration on quantum Heisenberg ferrimagnetic chains, revealing a discontinuous transition from ferrimagnetic to singlet states and identifying incommensurate correlations.

Contribution

It combines multiple computational methods to show how frustration alters phase transitions and spin correlations in ferrimagnetic chains.

Findings

Classical transition is destroyed by quantum fluctuations.

Discontinuous transition to singlet state occurs at high frustration.

Incommensurate short-range correlations emerge in the ferrimagnetic phase.

Abstract

We study the ground-state properties of weakly frustrated Heisenberg ferrimagnetic chains with nearest and next-nearest neighbor antiferromagnetic exchange interactions and two types of alternating sublattice spins S_1 > S_2, using 1/S spin-wave expansions, density-matrix renormalization group, and exact- diagonalization techniques. It is argued that the zero-point spin fluctuations completely destroy the classical commensurate- incommensurate continuous transition. Instead, the long-range ferrimagnetic state disappears through a discontinuous transition to a singlet state at a larger value of the frustration parameter. In the ferrimagnetic phase we find a disorder point marking the onset of incommensurate real-space short-range spin-spin correlations.