Direct visualization of ultrafast coupling between charge carriers and lattice degrees of freedom in photo-excited semiconductors has remained a long-standing challenge and is critical for understanding the light-induced physical behavior of materials under extreme non-equilibrium conditions. Here, by monitoring the evolution of the wave-vector resolved ultrafast electron diffraction intensity following above-bandgap photo-excitation, we obtain a direct visual of the structural dynamics in monocrystalline 2D perovskites. Analysis reveals a surprising, light-induced ultrafast lattice ordering resulting from a strong interaction between hot-carriers and the perovskite lattice, which induces an in-plane octahedra rotation, towards a more symmetric phase. Correlated ultrafast spectroscopy performed at the same carrier density as ultrafast electron diffraction reveals that the creation of a hot and dense electron-hole plasma triggers lattice ordering at short timescales by modulating the crystal cohesive energy. Finally, we show that the interaction between the carrier gas and the lattice can be altered by tailoring the rigidity of the 2D perovskite by choosing the appropriate organic spacer layer.
@article{arxiv.2204.01145,
title = {Direct visualization of ultrafast lattice ordering triggered by an electron-hole plasma in 2D perovskites},
author = {Hao Zhang and Wenbin Li and Joseph Essman and Claudio Quarti and Isaac Metcalf and Wei-Yi Chiang and Siraj Sidhik and Jin Hou and Austin Fehr and Andrew Attar and Ming-Fu Lin and Alexander Britz and Xiaozhe Shen and Stephan Link and Xijie Wang and Uwe Bergmann and Mercouri G. Kanatzidis and Claudine Katan and Jacky Even and Jean-Christophe Blancon and Aditya D. Mohite},
journal= {arXiv preprint arXiv:2204.01145},
year = {2022}
}