Nonlinearity enabled higher-order exceptional point | Prof. Meng Xiao

Microwave seminar | 19 February 2024
Prof. Meng Xiao
School of Physics, Wuhan University
Nonlinearity enabled higher-order exceptional point
Abstract
The role of nonlinearity on topology has been investigated extensively in Hermitian systems, while nonlinearity has only been used as a tuning knob in a PT-symmetric non-Hermitian system. Here, this talk shows that nonlinearity plays a crucial role in the topological classification of a non-Hermitian system. We start with a simple and intuitive example by demonstrating with both theory and circuit experiments an exceptional nexus, a higher-order exceptional point with a hybrid topological invariant, within only two coupled resonators with the aid of nonlinear gain.
The anisotropic critical behavior of the eigenspectra is verified with experiments. After that, we show that the eigenbasis of the Hamiltonian governing the system dynamics can still be complete at some nonlinear exceptional points. We present a circuit experiment to demonstrate one such NEP. Our findings lead to advances in understanding the peculiar features of nonlinear non-Hermitian systems, possibly opening new avenues for applications.
Main paper/arXiv, related to the seminar, and other references:
K. Bai, L. Fang, T. R. Liu, J. -Z. Li, D. Wan,* M. Xiao* NSR, 10, nwac259 (2022)
K. Bai, J. -Z. Li, T. R. Liu, L. Fang, D. Wan,* M. Xiao* PRL, 130, 266901 (2023)
K. Bai, T. R. Liu, L. Fang, J. -Z. Li, Chen Lin, D. Wan,* M. Xiao* PRL to be accepted (2024)
Prof. Meng Xiao received his BSc degree from Wuhan University in 2010, and his Ph. D. degree from the Hong Kong University of Science and Technology (HKUST) in 2014. After that, he had been working as a postdoc fellow with Prof. C. T. Chan in (HKUST) and Prof. Shanhui Fan (Stanford). He joined Wuhan University in 2018 .
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