The dynamics of a system having energy sources or drains can sometimes be approximated using a non-Hermitian Hamiltonian. The eigenvalue spectrum of a non-Hermitian lattice also fall into bands, not along the real axis, but on the complex plane. "Spectral topology" characterizes the shape of the shape of the spectrum on the complex plane, and is hence unique to non-Hermitian bands. Nontrivial spectral topology leads to physical phenomena such as the skin effect, the anomalous reflection, and characteristic features in impurity bound states. In this talk, I will introduce recent progress on the study of spectral topology in non-Hermitian bands.

References
K. Zhang, Z. Yang, and C. Fang, Phys. Rev. Lett. 125, 126402 (2020)
K. Zhang, Z. Yang*, and C. Fang, Nature Communications 13, 2496 (2022)
K. Zhang, C. Fang*, and Z. Yang, Phys. Rev. Lett. 131, 036402 (2023)
Zixi Fang, C. Fang*, and K. Zhang, Phys. Rev. B 108, 165132 (2023)