Beijing Institute of Mathematical Sciences and Applications

Zheng Wei Liu , Shing-Tung Yau , Hui Zhao

Chen Fang

Thursday, March 10, 2022 2:00 PM - 3:15 PM

JCY-1

In non-Hermitian bands, eigenvalues of the Hamiltonian become complex. The phase of the complex eigenvalue endows a new type of topology unique to non-Hermitian band theory, the spectral topology, describing the winding of the phase as the momentum goes along a loop in momentum space. In this talk, I show a special bulk-edge correspondence restricted to non-Hermitian bands: the spectral topology under periodic-boundary condition maps to the skin effect under open boundary condition. An algebraic method for quantifying the skin effect is introduced in 1D, and qualitative results on 2D and higher dimensions are also discussed. [1] K. Zhang, Z. Yang*, and C. Fang, arXiv:2102.05059 (2021) [2] K. Zhang, Z. Yang, and C. Fang, Phys. Rev. Lett. 125, 126402 (2020) [3] Z. Yang, K. Zhang, C. Fang, and J. Hu, Phys. Rev. Lett. 125, 226402 (2020)

Chen Fang graduated from Purdue University in 2011 with PhD degree. He worked as postdoc researcher at Princeton University and Massachusetts Institute of Technology from 2012 to 2015. He joined the faculty at Institute of Physics, Chinese Academy of Sciences in 2015. Chen Fang was a founder of the theory for "high-order" topological states in 2017 (Phys. Rev. Lett. 119, 246402), completed the topological classification of insulators having 230 space-group symmetries in 2018 (Nature Communications 9, 3530), and led the founding of the first computational database for topological materials in 2019 (Nature 566, 475). Recently, he became interested in new topics in condensed-matter physics such as non-Hermitian band theory and quantum-many-body scar.