Fluctuation-driven chiral ferromagnetism

TL;DR

This paper demonstrates how quantum fluctuations and spin-orbit couplings can stabilize chiral ferromagnetic phases with unique properties, expanding the understanding of ferromagnetism beyond classical predictions.

Contribution

It reveals fluctuation-stabilized chiral ferromagnetic phases driven by spin-orbit interactions, contrasting classical predictions of only collinear states.

Findings

Identification of fluctuation-stabilized chiral phases including ferromagnet with orbital chirality.

Observation of enhanced thermal Hall effect in chiral states.

Modification of classical phase diagram due to spin-orbit couplings.

Abstract

In general, quantum fluctuations are suppressed in ferromagnetic materials because they admit a simple unfrustrated ground state, greatly limiting the scope of phenomena that can be observed in these materials. In this work, we show how magnetization-non-conserving couplings fundamentally alter this paradigm by demonstrating the existence of a chiral ferromagnet that is stabilized by quantum fluctuations. More specifically, we show how these spin-orbit interactions modify the classical phase diagram; whereas a classical analysis predicts only collinear states, we observe fluctuation-stabilized phases, including a ferromagnet with large orbital chirality and a chiral stripe regime. We elucidate how such couplings spontaneously generate a scalar orbital chirality, in contrast to conventional mechanisms which rely upon a field-induced canting of vector chiral order. The resultant chiral states exhibit distinct transport signatures, namely an enhanced thermal Hall effect, and are of direct relevance to moir\'e heterostructures, Rydberg-atom arrays, and solid-state materials featuring non-Kramers spins.