Non-Hermitian control between absorption and transparency in perfect zero-reflection magnonics

Area of Science:

• Metamaterials and transformation optics
• Non-Hermitian physics

Background:

• Open systems in metamaterials exhibit exotic properties like perfect absorption/transmission and cloaking.
• Non-Hermitian physics describes open systems, but reflection characteristics in the complex frequency plane are under-explored.
• Zero-reflection (ZR) states are crucial for various applications.

Purpose of the Study:

• To demonstrate zero-reflection (ZR) states in the complex frequency plane for indirectly coupled two-magnon systems.
• To investigate non-Hermitian eigenmode hybridization and its relation to ZR states.
• To explore the tunability of absorption and transmission using these ZR states.

Main Methods:

• Theoretical investigation of indirectly coupled two-magnon systems.
• Analysis of reflection characteristics in the complex frequency plane.
• Characterization of perfect-zero-reflection (PZR) states and their properties.

Main Results:

• Demonstrated non-Hermitian eigenmode hybridization in the two-magnon system.
• Observed zero-reflection (ZR) states in the complex frequency plane.
• Identified perfect-ZR (PZR) states with pure real frequencies, exhibiting infinitely narrow reflection dips (~67 dB) and infinite group delay discontinuity.
• Showcased flexible tuning of absorption and transmission from nearly full absorption (NFA) to nearly full transmission (NFT).

Conclusions:

• Indirectly coupled two-magnon systems can exhibit both non-Hermitian eigenmode hybridization and ZR states.
• PZR states represent a distinct reflection singularity, tunable relative to resonant eigenstates.
• The findings enable flexible control over absorption and transmission, with potential applications in metamaterials and open systems.