Geometric Spin Rotation in Triangular Antiferromagnets

TL;DR

This paper uncovers a geometric phase phenomenon in triangular antiferromagnets where spin waves induce a permanent in-plane spin rotation, revealing a new way to control magnetic order through wave-induced geometric effects.

Contribution

It introduces the concept of geometric spin rotation caused by spin waves in frustrated magnets and provides an exact solution demonstrating this novel effect.

Findings

Spin waves can induce a geometric phase in antiferromagnets.

The phenomenon is analogous to parallel transport and wobbling coin.

Potential for controlling magnetic order via spin wave manipulation.

Abstract

We describe a geometric phenomenon in which a traveling wave made of degenerate Goldstone modes leaves behind a transformed ground state. In a triangular Heisenberg antiferromagnet, a pulse of circularly polarized spin waves rotates the spins within their plane. An exact solution of the nonlinear equations of motion demonstrates that the accumulated rotation is a geometric phase related to parallel transport of the order parameter. We point out a curious analogy between the motion of the magnetic order parameter and that of a wobbling coin. This phenomenon opens a new route for controlling antiferromagnetic order by spin waves and may extend to other frustrated magnets as well as other physical systems with noncommuting broken-symmetry generators.