Unidirectional perfect absorption induced by chiral coupling in spin-momentum locked waveguide magnonics

TL;DR

This paper demonstrates unidirectional perfect absorption in a chiral magnon-photon system using spin-momentum-locked waveguide modes, enabling controlled light-matter interactions for advanced signal processing.

Contribution

It introduces a novel platform combining chiral coupling with spin-momentum locking to achieve unidirectional perfect absorption in magnonics.

Findings

Achieved unidirectional perfect absorption via chiral magnon-photon coupling.

Demonstrated suppression of reflection and transmission at critical coupling.

Enabled bidirectional and multi-frequency absorption with additional YIG spheres.

Abstract

Chiral coupling opens new avenues for controlling and exploiting light-matter interactions. We demonstrate that chiral coupling can be utilized to achieve unidirectional perfect absorption. In our experiments, chiral magnon-photon coupling is realized by coupling the magnon modes in yttrium iron garnet (YIG) spheres with spin-momentum-locked waveguide modes supported by spoof surface plasmon polaritons (SSPPs). These photon modes exhibit transverse spin, with the spin direction determined by the propagation direction. Due to the intrinsic spin properties of the magnon mode, it exclusively couples with microwaves traveling in one direction, effectively suppressing the reflection channel. Under the critical coupling condition, transmission is also eliminated, resulting in unidirectional perfect absorption. By incorporating additional YIG spheres, bidirectional and multi-frequency perfect absorption can be achieved. Our work introduces a novel platform for exploring and harnessing chiral light-matter interactions within spin-momentum locked devices, offering a paradigm for unidirectional signal processing and energy harvesting technologies.