Enhanced Magnon Spin Current Using the Bosonic Klein Paradox

Efficient manipulation of magnons for information processing is a central topic in spintronics and magnonics. An outstanding challenge for long-distance spin transport with minimal dissipation is to over-come the relaxation of magnons and to amplify the spin current they carry. Here, we propose to amplify magnon currents based on the realization of the bosonic Klein paradox in magnetic nanostructures. This paradox involves the antimagnon, carrying opposite spin and energy, the existence of which is usually precluded by ferromagnetic instabilities, as it is an excitation at negative energy. We show that by appro-priately tuning the effective dissipation through spin-orbit torques, both magnons and antimagnons are dynamically stabilized. As a result, we find that the reflection coefficient of incident magnons at an inter-face between two coupled magnets can become larger than one, thereby amplifying the reflected magnon current. Our findings can lead to magnon amplifier devices for spintronic applications. Furthermore, our findings yield a solid-state platform to study the relativistic behavior of bosonic particles, which is an outstanding challenge with fundamental particles.

Automated summary

Efficient manipulation of magnons for information processing is crucial in spintronics and magnonics. This study proposes to amplify magnon currents by realizing the bosonic Klein paradox in magnetic nanostructures. The researchers successfully stabilize both magnons and antimagnons by tuning the effective dissipation using spin-orbit torques. This finding has potential applications in magnon amplifier devices for spintronic applications and provides a solid-state platform for studying the relativistic behavior of bosonic particles.