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arXiv · 2406.05168

Topological photonic alloy

Tiantao Qu·Mudi Wang·Xiaoyu Cheng·Xiaohan Cui·Ruo-Yang Zhang·Zhao-Qing Zhang·Lei Zhang·Jun Chen·C. T. Chan
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Abstract

We present the new concept of photonic alloy as a non-periodic topological material. By mixing non-magnetized and magnetized rods in a non-periodic 2D photonic crystal configuration, we realized photonic alloys in the microwave regime. Our experimental findings reveal that the photonic alloy sustains non-reciprocal chiral edge states (CESs) even at very low concentration of magnetized rods. The non-trivial topology and the associated edge states of these non-periodic systems can be characterized by the winding of the reflection phase. Our results indicate that the threshold concentrations for the investigated system within the first non-trivial band gap to exhibit topological behavior approach zero in the thermodynamic limit for substitutional alloys, while the threshold remains non-zero for interstitial alloys. At low concentration, the system exhibits an inhomogeneous structure characterized by isolated patches of non-percolating magnetic domains that are spaced far apart within a topologically trivial photonic crystal. Surprisingly, the system manifests CESs despite a local breakdown of time-reversal symmetry rather than a global one. Photonic alloys represent a new category of disordered topological materials, offering exciting opportunities for exploring topological materials with adjustable gaps.

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Tiantao Qu, Mudi Wang, Xiaoyu Cheng, Xiaohan Cui, Ruo-Yang Zhang, Zhao-Qing Zhang, Lei Zhang, Jun Chen, C. T. Chan. 2024-06-07. Topological photonic alloy. https://doi.org/10.1103/physrevlett.132.223802

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