Magnonic macroscopic quantum states and supercurrents (Prof. B. Hillebrands)

Elementary spin excitations - magnons (spin wave quanta) - open up a very promising direction. Magnons are bosons, and thus they are able to form spontaneously a spatially extended, coherent ground state, a Bose-Einstein condensate (BEC). The BEC can be conveniently created in a single-crystal film of yttrium iron garnet even at room temperature using parametric pumping. An extraordinary challenge is the use of this macroscopic quantum state for information transfer and processing. Recently we have succeeded to create a magnon supercurrent in such a macroscopic quantum state. I will present new, non-locally measured evidence for these supercurrents, discuss their properties, and I will provide an outlook toward potential future applications.