Using magnonic black holes to generate spin waves

• Suraj Pedada, Mechanical Engineering, Penn State Schreyer Honors College

• Jalil Manjarres, Physics and Astronomy, University of Delaware

Conventional electronic devices face critical processing speed limitations due to electron transport delays and joule heating within semiconductor channels. Magnonics offers a low-power alternative by utilizing collective spin-wave excitations (magnons) to process information without charge transit constraints. Here, we numerically demonstrate the computational realization of a magnonic black hole, spin-wave laser within a Permalloy nano-constriction using GPU-accelerated Mumax3 micromagnetic simulations. By driving a high-density, spin-polarized DC current through the geometry, convective spin-transfer torque (STT) introduces an asymmetric Doppler shift into the magnon dispersion relation. When local drift velocity exceeds a critical threshold, the magnon energy drops below zero, establishing a magnonic event horizon bounded by stable positive-energy regions. Spatiotemporal analysis of the underlying magnetization dynamics through simulation reveals that steady-state monochromatic lasing develops rapidly within nanoseconds. Fast Fourier Transform (FFT) spectral evaluation confirms stable, high-amplitude spin-wave emission with a single, sharp dominant mode. Furthermore, systematically modifying simulation constraints such as constriction geometry, applied current densities, and external in-plane magnetic fields affords robust dynamic control over the precise emission frequency while avoiding chaotic transitions. These results confirm that spin-wave amplification across artificial horizons serves as a viable mechanism for producing coherent magnons. This framework provides an essential foundation for the development of next-generation magnonic computing and wave-based logic circuits that operate at significantly higher processing speeds. Future efforts will map the methodology for targeting a discrete emission frequency and investigate experimental feasibility under real-world material damping, structural impurities, and localized thermal fluctuations.