Broad-wave-vector spin pumping of flat-band magnons

Spin pumping can generate spin current by driving a magnetic system into resonance, a phenomenon that can be electrically detected via the inverse spin Hall effect. However, the efficiency of spin current generation has remained limited, compared to that of spin-to-charge conversion. This work systematically demonstrates an innovative technique for electrically probing propagating spin waves and creating spin current with high efficiency, mediated by flat-band magnons excited by broad wave vectors. These findings lay a promising foundation for further experiments with propagating spin waves.