Second-harmonic generation in atomically thin Formula Presented and its possible origin from charge density wave transitions
Zhang R, Ruan W, Yu J, Gao L, Berger H, Forro L, Watanabe K, Taniguchi T, Ranjbar A, Belosludov R, Kühne TD, Bahramy MS, Xi X (2022)
Publication Type: Journal article
Publication year: 2022
Journal
Book Volume: 105
Article Number: 085409
Journal Issue: 8
DOI: 10.1103/PhysRevB.105.085409
Abstract
Optical second-harmonic generation (SHG) can only occur in noncentrosymmetric crystals in the leading electric-dipole approximation. Transition metal dichalco genides with the Formula Presented octahedral coordination is centrosymmetric, hence precluding SHG. Here we report the surprising observation of SHG in atomically thin Formula Presented, a prototypical charge density wave (CDW) material. Its intensity peaks in the trilayer, reaching 2% of that in monolayer Formula Presented, a two-dimensional crystal featuring pronounced nonlinear optical effect. The SHG signal exhibits a sixfold polarization dependence characteristic of a lattice with threefold rotational symmetry. It monotonically decreases with increasing temperature and persists at room temperature. Raman spectroscopy demonstrates that the CDW order is robust in atomically thin samples, with the transition temperature slightly lower than in the bulk. The SHG can be explained by the lattice distortion associated with the CDW as well as its fluctuation above the transition temperature. These results challenge the exciton insulator scenario and the chiral nature of the CDW, but support the band Jahn-Teller mechanism. Our work demonstrates SHG as a sensitive probe of the stacking order of the CDW in Formula Presented and enriches the material base for nonlinear optical effects.
Involved external institutions
Nanjing University
China (CN)
École Polytechnique Fédérale de Lausanne (EPFL)
Switzerland (CH)
National Institute of Materials Science (NIMS)
Japan (JP)
University of Manchester
United Kingdom (GB)
Universität Paderborn
Germany (DE)
Tohoku University
Japan (JP)
China (CN)
École Polytechnique Fédérale de Lausanne (EPFL)
Switzerland (CH)
National Institute of Materials Science (NIMS)
Japan (JP)
University of Manchester
United Kingdom (GB)
Universität Paderborn
Germany (DE)
Tohoku University
Japan (JP)
How to cite
APA:
Zhang, R., Ruan, W., Yu, J., Gao, L., Berger, H., Forro, L.,... Xi, X. (2022). Second-harmonic generation in atomically thin Formula Presented and its possible origin from charge density wave transitions. Physical Review B, 105(8). https://doi.org/10.1103/PhysRevB.105.085409
MLA:
Zhang, Ruiming, et al. "Second-harmonic generation in atomically thin Formula Presented and its possible origin from charge density wave transitions." Physical Review B 105.8 (2022).
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