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Coherent Phonon Catalysts: Lattice Vibrations Drive a Photoinduced Phase Transition in a Molecular Crystal

preprint
submitted on 15.01.2020 and posted on 20.01.2020 by Christopher Rich, Renee Frontiera
The atomic motions that make up phonons and molecular vibrations in molecular crystals influence their photophysical and electronic properties including polaron formation, carrier mobility, and phase transitions. Discriminating between spectator and driving motions is a significant challenge hindering optimization. Unlocking this information and developing fine-tuned controls over actively participating phonon modes would not only lead to a stronger understanding of photochemistry but also provide a significant new tool in controlling solid-state chemistry. We present a strategy using rationally-designed double pulses to enhance the yield of a photoinduced phase transition in a molecular crystal through coherent control of individual phonons. Using ultrafast spectroscopy, we identified 50 cm-1 and 90 cm-1 phonons responsible for the photoinduced spin-Peierls melting of potassium tetracyanoquinodimethane crystals. We show that the 90 cm-1 phonon can be used to catalyze the phase transition process while the 50 cm-1 phonon enhances the yield of the initial charge transfer reaction.

History

Email Address of Submitting Author

richc@umn.edu

Institution

University of Minnesota

Country

United States of America

ORCID For Submitting Author

0000-0002-3505-7643

Declaration of Conflict of Interest

The authors declare no conflict of interest.

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