Journal Home > Volume 14 , issue 1

The polarization selection rule of Raman scattering is crucial in symmetry analysis of elementary excitations in semiconductors and correlated electron systems. Here we reported the observation of breakdown of Raman selection rules in few-layer WS2 by using resonant Raman spectroscopy. When the excitation energy is close to the dark A exciton state, we observed some infrared active modes and backscattering forbidden modes. Importantly, we found that all observed phonon modes follow the same paralleled-polarization behavior. According to the electron-phonon coupling near the band edge in WS2, we proposed a theoretical model based on the intraband Fröhlich interaction. In this case, the polarization response of the scattering signal is no longer determined by the original Raman tensor of scattered phonons. Instead, it is determined by a new isotropic Raman tensor that generated from this intraband Fröhlich interaction between dark A exciton and phonons. We found that this theoretical model is in excellent agreement with the observed results. The breakdown of Raman selection rules can violate the conventional limitations of the optical response and provide an effective method to control the polarization of Raman scattering signals in two-dimensional materials.

File
12274_2020_3075_MOESM1_ESM.pdf (2.4 MB)
Publication history
Copyright
Acknowledgements
Rights and permissions

Publication history

Received: 06 July 2020
Revised: 16 August 2020
Accepted: 20 August 2020
Published: 05 January 2021
Issue date: January 2021

Copyright

© Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature

Acknowledgements

J. Z. and P. T. acknowledge support from the National Basic Research Program of China (nos. 2017YFA0303401 and 2016YFA0301200), Beijing Natural Science Foundation (No. JQ18014), and the Strategic Priority Research Program of the Chinese Academy of Sciences (No. XDB28000000).

Rights and permissions

Reprints and Permission requests may be sought directly from editorial office.
Email: nanores@tup.tsinghua.edu.cn

Return