Chiral spin pairing in helical magnets

TL;DR

This paper analyzes how specific interactions in frustrated spin systems lead to chiral spin pairings and two distinct phase transitions, resulting in complex magnetic states.

Contribution

It introduces a theoretical framework for understanding chiral spin pairing driven by phonon coupling in helical magnets, highlighting two successive phase transitions.

Findings

Chiral spin pairing is driven by Dzyaloshinskii-Moriya and Coulomb interactions.

Two second-order phase transitions occur upon cooling.

A chiral spin liquid state precedes helical magnetic order.

Abstract

The Ginzburg-Landau Hamiltonian for incommensurate frustrated classical spin systems is analyzed. The coupling to phonons through the Dzyaloshinskii-Moriya interaction and/or the four-spin exchange interaction of the Coulomb origin under the egde-sharing network of magnetic and ligand ions drive chiral spin piarings, introducing two successive second-order phase transitions upon cooling. First, a vector spin-chiral order appears with an either parity, leaving an O(2) chiral spin liquid. Then, the O(2) symmetry is broken by the spin ordering into a helical magnetic state. Possible candidate materials are also discussed.