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arXiv · 2401.09690

Third-order exceptional line in a nitrogen-vacancy spin system

Yang Wu·Yunhan Wang·Xiangyu Ye·Wenquan Liu·Zhibo Niu·Chang-Kui Duan·Ya Wang·Xing Rong·Jiangfeng Du
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Abstract

The exceptional points (EPs) aroused from the non-Hermiticity bring rich phenomena, such as exceptional nodal topologies, unidirectional invisibility, single-mode lasing, sensitivity enhancement and energy harvesting. Isolated high-order EPs have been observed to exhibit richer topological characteristics and better performance in sensing over 2nd-order EPs. Recently, high-order EP geometries, such as lines or rings formed entirely by high order EPs, are predicted to provide richer phenomena and advantages over stand-alone high-order EPs. However, experimental exploration of high-order EP geometries is hitherto beyond reach due to the demand of more degrees of freedom in the Hamiltonian's parameter space or a higher level of symmetries. Here we report the observation of the third-order exceptional line (EL) at the atomic scale. By introducing multiple symmetries, the emergence of the third-order EL has been successfully realized with a single electron spin of nitrogen-vacancy center in diamond. Furthermore, the behaviors of the EP structure under different symmetries are systematically investigated. The symmetries are shown to play essential roles in the occurrence of high-order EPs and the related EP geometries. Our work opens a new avenue to explore high-order EP-related topological physics at the atomic scale and to the potential applications of high-order EPs in quantum technologies.

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Yang Wu, Yunhan Wang, Xiangyu Ye, Wenquan Liu, Zhibo Niu, Chang-Kui Duan, Ya Wang, Xing Rong, Jiangfeng Du. 2024-01-18. Third-order exceptional line in a nitrogen-vacancy spin system. https://arxiv.org/abs/2401.09690

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