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Updated: Aug 23, 2025
High Resolution Phonon-assisted Quasi-resonance Fluorescence Spectroscopy
Published on: June 28, 2016
Ultrafast Spontaneous Localization of a Jahn-Teller Exciton Polaron in Two-Dimensional Semiconducting CrI3 by
Xufeng Li1, Aolei Wang2, Hailong Chen3
1State Key Laboratory of Modern Optical Instrumentation, Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou, Zhejiang310027, China.
Abstract:
The excited state species and properties in low-dimensional semiconductors can be completely redefined by electron-lattice coupling or a polaronic effect. Here, by combining ultrafast broadband pump-probe spectroscopy and first-principles GW and Bethe-Salpeter equation calculations, we show semiconducting CrI3 as a prototypical 2D polaronic system with characteristic Jahn-Teller exciton polaron induced by symmetry breaking. A photogenerated electron and hole in CrI3 localize spontaneously in ∼0.9 ps and pair geminately to a Jahn-Teller exciton polaron with elongated Cr-I octahedra, large binding energy, and an unprecedentedly small exciton-exciton annihilation rate constant (∼10-20 cm3 s-1). Coherent phonon dynamics indicates the localization is mainly triggered by the coherent nuclear vibration of the I-Cr-I out-of-plane stretch mode at 128.5 ± 0.1 cm-1. The excited state Jahn-Teller exciton polaron in CrI3 broadens the realm of 2D polaron systems and reveals the decisive role of coupled electron-lattice motion on excited state properties and exciton physics in 2D semiconductors.
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