Frequency-division routing via spin-refractive-index locking

Yuan-Peng Peng; Shi-Yao Zhu; J Q You; Yi-Pu Wang

doi:10.1038/s41467-026-70460-w

Frequency-division routing via spin-refractive-index locking

Nat Commun. 2026 Mar 7;17(1):3637. doi: 10.1038/s41467-026-70460-w.

Authors

Yuan-Peng Peng¹, Shi-Yao Zhu^{1

2

3}, J Q You^{4

5}, Yi-Pu Wang⁶

Affiliations

¹ Zhejiang Key Laboratory of Micro-Nano Quantum Chips and Quantum Control, State Key Laboratory for Extreme Photonics and Instrumentation, School of Physics, Zhejiang University, Hangzhou, China.
² College of Optical Science and Engineering, Zhejiang University, Hangzhou, China.
³ Hefei National Laboratory, Hefei, China.
⁴ Zhejiang Key Laboratory of Micro-Nano Quantum Chips and Quantum Control, State Key Laboratory for Extreme Photonics and Instrumentation, School of Physics, Zhejiang University, Hangzhou, China. jqyou@zju.edu.cn.
⁵ College of Optical Science and Engineering, Zhejiang University, Hangzhou, China. jqyou@zju.edu.cn.
⁶ Zhejiang Key Laboratory of Micro-Nano Quantum Chips and Quantum Control, State Key Laboratory for Extreme Photonics and Instrumentation, School of Physics, Zhejiang University, Hangzhou, China. yipuwang@zju.edu.cn.

Abstract

Here we demonstrate spin-refractive-index locking (SRIL) in a composite right-left-handed transmission-line metamaterial, where the transverse spin of surface modes is locked to the sign of the effective refractive index. Unlike conventional spin-momentum locking (SML), the SRIL reverses the spin for the same energy propagation direction in right- and left-handed bands. Using this index-dependent spin control, we realize frequency-selective chiral photon-magnon interaction by placing a yttrium iron garnet (YIG) sphere above the metamaterial and achieving strong nonreciprocity, where magnons only couple to microwaves of matching spin and the required direction is determined by the operating band. Tuning the frequency across the two bands dynamically switches the coupling direction, enabling a compact, reconfigurable on-chip routing device for spin-selective microwave control and nonreciprocal signal processing.