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Published April 18, 2018 | Supplemental Material
Journal Article Open

Strongly Coupled Electron–Phonon Dynamics in Few-Layer TiSe_2 Exfoliates

Abstract

Ultrafast electron diffraction is used to probe the time-resolved dynamics in a few-layer TiSe_2 sample. At normal incidence, the suppression of the Bragg diffraction peak intensities following photoexcitation displays strongly biexponential behavior. For tilted samples, changes in the diffraction peak positions reveal coherent acoustic vibrations that are dependent on the sample thickness and that further permit a calculation of the Young's modulus. The complex room temperature lattice dynamics observed are attributed to strong electron–phonon coupling and electron–lattice equilibration processes, which support a Jahn–Teller origin of the charge density wave behavior in TiSe_2. Additionally, the significant role that the related Kohn anomalies may play in the electron transport dynamics and transition mechanism of this material is emphasized. These results demonstrate the importance of strongly coupled electron–phonon dynamics in the relaxation of electronically excited room temperature TiSe2, which is expected to impact its applicability in optoelectronics.

Additional Information

© 2018 American Chemical Society. Received: August 4, 2017; Published: February 7, 2018. Generous financial support for this work was provided by the Gordon and Betty Moore Foundation, as well as the National Science Foundation and the Air Force Office of Scientific Research (grant FA9550-16-1-0200). J.H. acknowledges the support from China 1000-Young Talents Plan. The authors gratefully acknowledge Professor Austin Minnich and Dr. Spencer J. Baskin for valuable discussions, and dedicate this manuscript to the memory of our colleague and mentor Professor Ahmed H. Zewail. Author Contributions: The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. The authors declare no competing financial interest.

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