First-principles based simulation on radiative exciton-exciton annihilation of excitons in two-dimensional transition metal dichalcogenides

Ching-Hung Shih^1*, Ping-Yuan Lo², Chao-Hsin Chien¹, Shao-Yu Chen^3,4, Shun-Jen Cheng²

¹Institute of Electronics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
²Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
³Center for Condensed Matter Sciences, National Taiwan University, Taipei, Taiwan
⁴Center of Atomic Initiative for New Material, National Taiwan University, Taipei, Taiwan

* Presenter:Ching-Hung Shih, email:shih2356585@gmail.com

Exciton–exciton annihilation (EEA) is a process that violates particle number conservation while preserving energy. It occurs when two excitons interact, one electron–hole pair recombine and transfer its energy to the other, thereby exciting it to a higher energy state. Earlier studies primarily reported non-radiative EEA in monolayer transition metal dichalcogenides (TMDs) [1,2]. However, recent work has revealed the presence of radiative EEA in multilayer TMD systems, accompanied by intense photoluminescence (PL) signals [3]. This observation unveils the potential of EEA to be applied in next-generation optoelectronic devices.

In this work, we utilize our first-principles based Bethe–Salpeter equation code (WannierBSE) [4] to simulate the exciton energy landscape and identify the conditions under which EEA occurs. We further explain the differences between the mechanism of EEA and that of conventional spontaneous emission. Finally, we demonstrate that, under certain conditions, the transition rate of EEA can exceed the exciton lifetime, making it the dominant mechanism in the system.

[1] N. Kumar, Q. Cui, F. Ceballos, D. He, Y. Wang, and H. Zhao, Phys. Rev. B 89, 125427 (2014).
[2] D. Sun, Y. Rao, G. A. Reider, G. Chen, Y. You, L. Brezin, A. R. Harutyunyan, and T. F. Heinz, Nano Lett. 14, 10, 5625–5629 (2014).
[3] Y. H. Chen et al. Nat. Commun. 16, 2935 (2025).
[4] https://quantum.web.nycu.edu.tw/wannierbse/

Keywords: Exciton-exciton annihilation, First-principles calculations, Bethe-Salpeter equation, Transition metal dichalcogenides