Coherent Lattice Vibrations in Mono- and Few-Layer WSe2

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• 作者：Tae Young Jeong ; Byung Moon Jin ; Sonny H. Rhim ; Lamjed Debbichi ; Jaesung Park ; Yu Dong Jang ; Hyang Rok Lee ; Dong-Hun Chae ; Donghan Lee ; Yong-Hoon Kim ; Suyong Jung ; Ki Ju Yee
• 刊名：ACS Nano
• 出版年：2016
• 出版时间：May 24, 2016
• 年：2016
• 卷：10
• 期：5
• 页码：5560-5566
• 全文大小：432K
• 年卷期：0
• ISSN：1936-086X

文摘

We report the observation of coherent lattice vibrations in mono- and few-layer WSe₂ in the time domain, which were obtained by performing time-resolved transmission measurements. Upon the excitation of ultrashort pulses with the energy resonant to that of A excitons, coherent oscillations of the A_1g optical phonon and longitudinal acoustic phonon at the M point of the Brillouin zone (LA(M)) were impulsively generated in monolayer WSe₂. In multilayer WSe₂ flakes, the interlayer breathing mode (B₁) is found to be sensitive to the number of layers, demonstrating its usefulness in characterizing layered transition metal dichalcogenide materials. On the basis of temperature-dependent measurements, we find that the A_1g optical phonon mode decays into two acoustic phonons through the anharmonic decay process.