Ripple state in the frustrated honeycomb-lattice antiferromagnet

TL;DR

This paper introduces the 'ripple state', a novel low-temperature phase in a frustrated honeycomb-lattice antiferromagnet, characterized by a ring-like degeneracy and a water ripple-like spin texture, with potential multiferroic implications.

Contribution

It reports the discovery of a new multiple-q state called the ripple state in a frustrated honeycomb-lattice Heisenberg antiferromagnet, revealing a second-order phase transition from a ring-liquid state.

Findings

Identified the ripple state as a new thermodynamic phase.

Demonstrated the transition from ring-liquid to ripple state.

Linked the ripple state to potential electric polarization vortices.

Abstract

We discover a new type of multiple-$q$ state, "ripple state", in a frustrated honeycomb-lattice Heisenberg antiferromagnet under magnetic fields. The ground state has an infinite ring-like degeneracy in the wavevector space, exhibiting a cooperative paramagnetic state, "ring-liquid" state. We elucidate that the system exhibits the ripple state as a new low-temperature thermodynamic phase via a second-order phase transition from the ring-liquid state, keeping the ring-like spin structure factor. The spin texture in real space looks like a "water ripple" and can induce a giant electric polarization vortex. Possible relationship to the honeycomb-lattice compound, ${\rm Bi_{3}Mn_{4}O_{12}(NO_{3})}$, is discussed.