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Nano Research

Article Title

Breakdown of Raman selection rules by Fröhlich interaction in few-layer WS2

Authors

Qing-Hai Tan, State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Center of Materials Science and Optoelectronics Engineering, CAS Center of Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100083, China
Yu-Jia Sun, State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Center of Materials Science and Optoelectronics Engineering, CAS Center of Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100083, China
Xue-Lu Liu, State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Center of Materials Science and Optoelectronics Engineering, CAS Center of Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100083, China
Kai-Xuan Xu, State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Center of Materials Science and Optoelectronics Engineering, CAS Center of Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100083, China
Yuan-Fei Gao, State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Center of Materials Science and Optoelectronics Engineering, CAS Center of Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100083, China;Beijing Academy of Quantum Information Science, Beijing 100193, China
Shu-Liang Ren, State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Center of Materials Science and Optoelectronics Engineering, CAS Center of Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100083, China
Ping-Heng Tan, State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Center of Materials Science and Optoelectronics Engineering, CAS Center of Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100083, China;Beijing Academy of Quantum Information Science, Beijing 100193, China
Jun Zhang, State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Center of Materials Science and Optoelectronics Engineering, CAS Center of Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100083, China;Beijing Academy of Quantum Information Science, Beijing 100193, China

Keywords

WS2, resonant Raman scattering, dark exciton, Raman section rules, Fröhlich interaction

Abstract

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.

Publisher

Tsinghua University Press

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