Direct evidence for efficient carrier multiplication in the topological insulator Bi$_2$Se$_3$

• DOI: 10.48550/arxiv.2405.01323
• Publication Date: 2024-05-02
• Authors: Michael Herb; Leonard Weigl; Niklas Hofman; Johannes Gradl; Jason F. Khoury; Leslie M. Schoop; Isabella Gierz
• Keywords: Topological insulator

Carrier multiplication (CM), where the absorption of a single photon results in generation several electron-hole pairs via impact ionization, plays pivotal role quest for enhancing performance solar cells beyond Shockley-Queisser limit. The combination its narrow bandgap relative to energy visible light, along with low phonon frequencies that hinder efficient dissipation into phonons, makes topological insulator Bi$_2$Se$_3$ an optimal candidate material CM. Here we use time- and angle-resolved photoemission spectroscopy (trARPES) trace number after photoexcitation pump pulses at $\hbar\omega=2$ eV. We find both electrons inside conduction band as well holes valence keep increasing long pulse is gone, providing direct evidence also analyze transient structure hot carrier dynamics band, complete picture non-equilibrium photoexcited which can now serve basis novel optoelectronic applications.