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Author: Kai Hao
Requested Type: Oral
Submitted: 2015-04-24 22:18:45

Co-authors: Galan Moody, Chandriker Dass, Chang-Hsiao Chen, Lain-Jong Li, Akshay Singh,Kha Tran, Genevieve Clark, Xiaodong Xu, Gunnar Berg, Ermin Malic, Andreas Knorr, Xiaoqin Li

Contact Info:
University of Texas at Austin
Department of Physics 2515 Spe
Austin, TX   78712

Abstract Text:
Excitons in monolayer transition metal dichalcogenides (TMDCs) exhibit exceptionally large binding energy, strong optical absorption, and spin valley coupling. These characteristics make TMDCs a promising system for optoelectronics and valleytronics. An important yet unknown property of excitons in TMDCs is the intrinsic homogeneous linewidth, which reflect radiative recombination and irreversible dissipative decay. Here, we use optical coherent two-dimensional spectroscopy to reveal the exciton homogeneous linewidth in monolayer CVD grown Tungsten Diselenide (WSe2). With excitation density and temperature dependent measurements, exciton- exciton interaction and exciton-phonon interactions are quantitatively evaluated. Extrapolating to zero density and temperature, we obtain a residual homogeneous linewidth of ∼ 1.5 meV, which places a lower bound of 0.2 ps on the exciton radiative lifetime. This result is consistent with microscopic calculations, which suggest that fast radiative decay of delocalized excitons arises from their large oscillator strength.