[NCTS Lecture Series] Many-body correlation effects in electron-phonon coupled and excitonic quantum materials
Title: [NCTS Lecture Series] Many-body correlation effects in electron-phonon coupled and excitonic quantum materials
Speaker: Prof. Zhenglu Li (University of Southern California)
Time: 2025/5/21 (Wed.) 14:20-15:20
Place: NCTS Physics Lecture Hall, 4F, Cosmology Hall, NTU
Abstract
Accurate ab initio treatment of many-body interactions is essential to the understanding of excitations and dynamics of quantum materials. Within the framework of many-body perturbation theory, this talk focuses on unveiling correlation effects in two types of phenomena: 1) electron-phonon coupling in oxides and kagome metals, and 2) Wigner crystalline excitons in two-dimensional moiré superlattices. In the first part of the talk, using the recently developed GW perturbation theory [1, 2], our results show that many-electron correlations can significantly enhance the electron-phonon coupling in bismuthate Ba1-xBixO3 [1] and cuprate La2-xSrxCuO4 [3]. Our systematic calculations also reveal the critical role of electron-phonon coupling in infinite-layer nickelate Nd1-xSrxNiO2 [4] and kagome metal CsV3Sb5 [5]. The second part of the talk will discuss how excitons arise from strongly correlated generalized Wigner-crystal ground states in moiré superlattices, using the GW-Bethe-Salpeter equation approach. Our results [6] surprisingly uncover the propagation of correlation effects from ground states to excited states, and the two-particle excitonic correlations utterly dominate over the kinetic energy of the free electron-hole pairs. Our study provides an unambiguous microscopic understanding of the strongly correlated Wigner crystalline excitons, suggesting them as a highly tunable platform to study mixed boson-fermion many-body interactions.References
[1] Z. Li, G. Antonius, M. Wu, F. H. da Jornada, S. G. Louie, Phys. Rev. Lett. 122, 186402 (2019).
[2] Z. Li, G. Antonius, Y.-H. Chan, S. G. Louie, Comput. Phys. Commun. 295, 109003 (2024).
[3] Z. Li, M. Wu, Y.-H. Chan, S. G. Louie, Phys. Rev. Lett. 126, 146401 (2021).
[4] Z. Li, S. G. Louie, Phys. Rev. Lett. 133, 126402 (2024).
[5] J.-Y. You, C.-E. Hsu, M. Del Ben, Z. Li, Phys. Rev. Lett. 134, 106401 (2025).
[6] J.-Y. You, C.-E. Hsu, Z. Zhu, B. Zhang, Z. Ye, M. H. Naik, T. Cao, H.-C. Hsueh, S. G. Louie, M. Del Ben, Z. Li, manuscript in preparation (2025).
