Stephen Hawking's 1974 prediction that quantum effects near the event horizon enable black holes to emit thermal radiation — meaning that they are not completely black — could provide a fascinating experimental means for probing the intersection of general relativity and quantum mechanics. Sadly, however, the temperatures associated with Hawking radiation from astrophysical black holes are far too small to be detectable within the foreseeable future. But a proposal by Alejandro Roldán-Molina and colleagues could allow the physics of Hawking radiation to be probed inside magnetic materials.
Although astrophysical black holes may be out of experimental reach, analogues of black hole horizons can and have been created for sound waves, based on transitions between subsonic and supersonic flow. Roldán-Molina et al. showed theoretically that a similar analogy can be applied to magnetic systems, with the interactions between spin currents and magnetization dynamics giving rise to black- or white-hole horizons for magnons — the quanta of spin waves. As the predicted Hawking temperatures could be as large as 1 K, magnonic black holes could provide an experimentally accessible means for probing Hawking radiation physics in the solid state.
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Fleet, L. Black holes: New horizons for magnonics. Nature Phys 13, 205 (2017). https://doi.org/10.1038/nphys4067