Emergent spatiotemporal order and nonreciprocity in driven-dissipative nonlinear magnetic systems

TL;DR

This paper demonstrates how driven-dissipative nonlinear magnetic systems can spontaneously form nonreciprocal, spacetime-symmetry-breaking states, enabling novel transport phenomena, phase transitions, and analogue gravity effects in a controllable, tabletop setting.

Contribution

It reveals a ferromagnetic multilayer platform that stabilizes a nonequilibrium condensate with emergent nonreciprocity and spacetime order, connecting nonlinear magnetization dynamics to non-Hermitian physics and analogue gravity.

Findings

Realization of a spin superfluid diode with asymmetric magnon propagation.

Flow-borne nonreciprocity without structural asymmetry or fine-tuning.

Generation of sonic horizons and Hawking-like magnon emission.

Abstract

The identification of platforms with independently tunable nonlinearity and non-Hermiticity promises a quantitative route to far-from-equilibrium universality across many-body systems. Here we show that a conventional ferromagnetic multilayer realizes this paradigm: balancing a dc drive against Gilbert damping stabilizes a self-organized, current-carrying nonequilibrium condensate that spontaneously breaks spacetime-translation symmetry. The chirality of this spin superfluid limit cycle state generates an inherently nonreciprocal flow: long-wavelength magnons of opposite chirality acquire asymmetric dispersions and propagate direction-selectively, realizing a spin superfluid diode. This asymmetry is flow-borne -- it reflects broken Galilean invariance and requires neither structural asymmetry nor finely tuned gain-loss balance. Linearized dynamics in the comoving superfluid frame are intrinsically pseudo-Hermitian and, in the long-wavelength sector, can be mapped to a (1+1)D wave equation on curved spacetime. Spatial modulation of the drive enables the generation of sonic horizons that parametrically squeeze magnons and produce Hawking-like particle-hole emission. Our results establish a tabletop route from nonlinear dissipative-driven magnetization dynamics to nonreciprocal transport, nonequilibrium phase transitions, and analogue-gravity kinematics.