Magnons and Antimagnons: Engineering Dissipation to Explore the Limits of Nonequilibrium Magnetism

Objectif

Magnons are the quantized bosonic excitations of a magnetic system. In contrast to most other bosonic systems, their maximum population is intrinsically limited by the total number of magnetic moments (spins) in the systems. Our recent experiments demonstrate that the magnon population can be saturated – consistent with a population inversion of the spin system – by electrically controlling dissipation, leading to a dynamically stabilized inverted magnetization state. Theory works predict that the excitations of this state are magnons with opposite chirality that carry negative angular momentum, so-called antimagnons. The interaction between magnons and antimagnons enables the study of highly unusual effects, arising in presence of spatially inhomogeneous dissipation, such as the magnonic Klein paradox, magnon black-hole horizons, and magnon lasing. Nonequlibrium magnonics thus promises, for the first time, a solid-state platform governed by Bose statistics to test concepts rooted in high-energy physics. The aim of MERLIN is to experimentally pioneer the emerging field of deep-nonequilibrium magnonics (or antimagnonics), breaking new ground in nonequilibrium physics. I will explore the potential of antimagnons for future magnonic devices and advance the understanding of bosonic transport driven by quasi-equilibrium chemical potentials. First, I will exploit the established electrical control over dissipation to elucidate the properties of antimagnons by performing electrical and optical spectroscopy of the switched state. Second, I will elucidate the interaction between a localized nonequilibrium region hosting antimagnons and the equilibrium magnons in an extended magnetic layer. Third, I will reveal magnon-antimagnon correlations with potential for remote entanglement and magnonic amplifiers. Overall, MERLIN will provide breakthroughs at the frontier of magnonics by controlling dissipation, with far-reaching implications for innovative magnonic device schemes.