Kai Zhang | 张锴

About Me

My primary research interests are in non-Hermitian physics and open quantum systems. My current work focuses on establishing non-Hermitian band theory and investigating dynamic phenomena driven by the non-Hermitian skin effect, which may be realized in classical wave systems such as photonic, acoustic, and mechanical platforms. Since non-Hermitian physics intrinsically deals with the dynamics of open systems, several important questions emerge after developing the foundational non-Hermitian band theory: What novel non-Hermitian effects exist, and how can these phenomena be understood in quantum systems, such as Fermi liquids and strongly correlated systems? Within the framework of the master equation, how can we elucidate the dynamical processes in non-equilibrium quantum systems? Can non-Hermitian physics provide an effective framework for understanding and solving non-equilibrium problems? Building on the insights from non-Hermitian band theory, my research seeks to address these questions and explore new directions for advancing the study of open quantum systems.

Employment

2022.09 ~ present -- University of Michigan, Postdoctoral Research Fellow in Physics Department (advisor: Kai Sun)

Education

2017.09 ~ 2022.06 -- Institute of Physics, Chinese Academy of Sciences, Ph.D. degree (advisor: Chen Fang)
2013.09 ~ 2017.06 -- Liaoning Technical University, B.Sc. in Physics (advisor: Yong-Jun Zhang)

Academic Service

Reviewed for Journal: Physical Review Letters, Nature Communications, Communications Physics, etc.

Academic Honors/Awards

2022 ~ 2023 -- Excellent Doctoral Dissertation Award, CAS
2021 -- National Scholarship for Doctoral Students, UCAS
2020 ~ 2021 -- Excellent Prize of Presidential Scholarship, CAS

Areas of Interest

Non-Hermitian physics, Nonequilibrium quantum dynamics, Open quantum systems, Topological phases of matter, Periodically driven systems, Metamaterials

Publications

(The superscript * indicates the first author, and † denotes the corresponding author)

Google Scholar; ResearchGate; ORCID;

I. Topological origin of low-dimensioanl non-Hermitian skin effect

1. "Correspondence between winding numbers and skin modes in non-Hermitian systems", K Zhang*, Z Yang*, C Fang, Physical Review Letters 125 (12), 126402 (2020)
2. "Non-Hermitian bulk-boundary correspondence and auxiliary generalized Brillouin zone theory", Z Yang*, K Zhang*, C Fang, J Hu, Physical Review Letters 125 (22), 226402 (2020)

II. Geometry dependency and universality of higher-dimensional non-Hermitian skin effect

3. "Universal non-Hermitian skin effect in two and higher dimensions", K Zhang, Z Yang, C Fang, Nature communications 13 (1), 2496 (2022)
4. "Universal spectral moment theorem and its applications in non-Hermitian systems", N Cheng, C Shu, K Zhang, X Mao, K Sun, Physical Review Letters 133 (21), 216401 (2024)
5. "Two-dimensional Asymptotic Generalized Brillouin Zone Conjecture", Z Xu, B Pang, K Zhang^†, Z Yang^†, arXiv:2311.16868 (2023)

III. Anisotropic wavepacket dynamics in non-Hermitian band systems

6. "Dynamical degeneracy splitting and directional invisibility in non-Hermitian systems", K Zhang, C Fang, Z Yang, Physical Review Letters 131 (3), 036402 (2023)
7. "Geometry-dependent skin effect and anisotropic Bloch oscillations in a non-Hermitian optical lattice", Y Qin, K Zhang^†, L Li^†, Physical Review A 109 (2), 023317 (2024)
8. "Observation of the geometry-dependent skin effect and dynamical degeneracy splitting", T Wan, K Zhang, J Li, Z Yang, Z Yang, Science Bulletin (2023)

IV. Quasi-long-range algebraic decay in non-Hermitian systems

9. "Algebraic non-Hermitian skin effect and unified non-Bloch band theory in arbitrary dimensions", K Zhang, C Shu, and K Sun, arXiv:2406.06682 (2024)
10. "Edge theory of the non-Hermitian skin modes in higher dimensions", K Zhang, Z Yang, K Sun, Physical Review B 109 (16), 165127 (2024)
11. "Ultra spectral sensitivity and non-local bi-impurity bound states from quasi-long-range non-hermitian skin modes", C Shu, K Zhang^†, K Sun^†, arXiv:2409.13623 (2024)

V. Impurity states in non-reciprocal systems

12. "Point-Gap Bound States in Non-Hermitian Systems", Z Fang, C Fang^†, K Zhang^†, Physical Review B 108, 165132 (2023)
13. "Tailoring Bound State Geometry in High-Dimensional Non-Hermitian Systems", A Yang, Z Fang, K Zhang^†, C Fang^†, arXiv:2406.07626 (2024)
14. "Magnetochiral Charge Pumping due to Charge Trapping and Skin Effects in Chirality-Induced Spin Selectivity", Y Zhao*, K Zhang*, J Xiao, K Sun, and B Yan, arXiv:2201.03623, accepted by Nature Communications (2024)

VI. Non-equilibrium physics: open quantum and periodically driven systems

15. "Loss-induced universal one-way transport in periodically driven systems", C Shu, K Zhang^†, K Sun^†, Physical Review B 109 (18), 184302 (2024)
16. "Helical damping and dynamical critical skin effect in open quantum systems", CH Liu, K Zhang, Z Yang, S Chen, Physical Review Research 2 (4), 043167 (2020)

VII. Non-Hermitian degeneracies in few-level and band systems

17. "Polariton-driven Reentry and Anisotropic Exceptional Points in PT-symmetric Ternary System", C Lee*, K Zhang*, J Miao, K Sun, H Deng, Physical Review A 109 (5), 053503 (2024)
18. "Non-Bloch Dirac Points and Phase Diagram in the Stacked Non-Hermitian SSH Model", M Schoenzeit, C Shu, K Zhang, K Sun

Contact Information

Email: phykai@umich.edu (zkai.phy@gmail.com)
Mobile: +17348829477 (+8615510219703)
Address: 1114 Maiden Lane Court, Ann Arbor, MI, 48105