Thermal Spin Waves from Accelerating Domain Walls via the Unruh Effect

TL;DR

This paper demonstrates that accelerating magnetic domain walls can emit spin waves with a thermal spectrum analogous to the Unruh effect, linking relativistic quantum phenomena with magnetic systems and suggesting new ways to entangle magnetic textures.

Contribution

It introduces a method to observe the Unruh effect through domain wall acceleration in magnetic materials, connecting relativistic quantum field theory with condensed matter physics.

Findings

Domain wall acceleration produces a thermal spin wave spectrum.

The emission spectrum is characterized by an effective Unruh temperature.

Magnetism can serve as a platform for exploring relativistic quantum effects.

Abstract

We consider a wire consisting of a conducting ferromagnetic layer and an insulating antiferromagnetic layer that are coupled. The ferromagnet hosts a domain wall, which is dynamically driven by a charge current. We show that for a specific time-dependent current, the domain wall moves according to a Rindler trajectory. This motion excites spin waves in the antiferromagnetic insulator, and their emission spectrum is characterised by an effective temperature analogous to the Unruh temperature, $T_U = \hbar a/2\pi c k_B$, with a the acceleration of the domain wall, c the maximum antiferromagnetic spin wave velocity, and kB the Boltzmann constant. This thermal signature is a direct consequence of the Unruh effect and could be experimentally observed. Our results establish magnetism as a promising platform for probing relativistic quantum field phenomena. Moreover, since the Unruh effect is inherently linked to entanglement, our proposal provides a route for entangling magnetic domain walls via relativistic effects.