Lineshape characterization of excitons in monolayer WS2 by two-dimensional electronic spectroscopy

• Published in: Nanoscale advances 2020-06, Vol.2 (6), p.2333-2338
• Main Authors: Guo, Liang, Chen, Chun-An, Zhang, Zhuquan, Monahan, Daniele M, Lee, Yi-Hsien, Fleming, Graham R
• Format: Article
• Language: English
• Subjects: Chemistry
• ISSN: 2516-0230
• DOI: 10.1039/d0na00240b

The optical properties of monolayer transition metal dichalcogenides (TMDCs), an important family of two-dimensional (2D) semiconductors for optoelectronic applications, are dominated by two excitons A (XA) and B (XB) located at K/K's valleys. The lineshape of the excitons is an indicator of the interaction of the excitons with other particles and also largely determines the performance of TMDC-based optoelectronic devices. In this work, we apply 2D electronic spectroscopy (2DES), which enables separation of the intrinsic homogeneous linewidth and the extrinsic inhomogeneous linewidth, to dissect the lineshape of XA in monolayer WS 2 . With a home-built broadband optical parametric amplifier, the 2D spectra give the exciton linewidth values for extensive ranges of excitation densities and temperatures, reflecting inter-exciton and exciton–phonon interactions. Meanwhile, the time-domain evolution of the lineshape reveals a similar rate of spectral diffusion to that in quantum wells (QWs) based on III–V semiconductors. Two-dimensional electronic spectroscopy (2DES) provides dual perspectives for characterizing exciton lineshape in monolayer transition metal dichalcogenides (TMDCs), allowing discrimination of homogeneous and inhomogeneous linewidths.