Realization of Multifunctional Bosonic Magnon Transistor via Thermal Phonon Gating

Abstract

Magnons have demonstrated enormous potential for next‐generation information technology, namely the ability to build quasiparticle low‐power integrated circuits without the moving of electrons. An experimental bosonic magnon transistor with multifunction, low‐loss, and full‐wavelength control of propagating spin waves (magnon current) is developed in this work. Using a monolayer of graphene as the high‐efficiency thermal phonon source and a low‐loss electrically insulating ferrimagnetic single‐crystalline yttrium iron garnet film as the propagating spin‐wave channel, the presented transistor has three functioning regions of spin‐wave modulation at full wavelength: prominent amplification, complete cut‐off, and linear phase shift. The magnon‐phonon‐mediated nonequilibrium state created by the temperature gradient in this transistor works in two ways: when the thermal phonon flow is small, the positive thermal spin‐torque induced by the longitudinal spin‐Seebeck effect amplifies spin waves; when the thermal phonon flow is large, the magnon–magnon interaction due to nonequilibrium thermal magnon injection greatly contributes to spin‐wave cut‐off. Furthermore, linear adjustment of the spin‐wave phase by creating a thermal phonon bath is demonstrated. These findings reveal that the numerous magnon–phonon coupling mechanisms in magnetic insulators offer a promising platform for the implementation of reconfigurable magnonic transistors.