Codimension-Two Spiral Spin-Liquid in the Effective Honeycomb-Lattice Compound Cs$_3$Fe$_2$Cl$_9$

TL;DR

This paper reports the discovery of a codimension-two spiral spin-liquid in Cs$_3$Fe$_2$Cl$_9$, revealing a new route to such states by overcoming weak further-neighbor interactions, with complex magnetic orderings observed under magnetic fields.

Contribution

The study demonstrates the existence of a codimension-two spiral spin-liquid in an effective honeycomb lattice, combining neutron scattering and simulations to reveal novel magnetic phenomena.

Findings

Identification of a spiral spin-liquid state in Cs$_3$Fe$_2$Cl$_9$

Observation of competing spiral and spin density wave orders

Possible order-by-disorder transition under magnetic field

Abstract

A codimension-two spiral spin-liquid is a correlated paramagnetic state with one-dimensional ground state degeneracy hosted within a three-dimensional lattice. Here, via neutron scattering experiments and numerical simulations, we establish the existence of a codimension-two spiral spin-liquid in the effective honeycomb-lattice compound Cs$_3$Fe$_2$Cl$_9$, which demonstrates a novel path to spiral spin-liquids by overcoming the long-standing impediment of weak further-neighbor interactions. In the long-range ordered regime, competing spiral and spin density wave orders emerge as a function of applied magnetic field, among which a possible order-by-disorder transition is identified.