title: The In-Plane Anisotropy of WTe2 Investigated by Angle-Dependent and Polarized Raman Spectroscopy.
abstract: Tungsten ditelluride (WTe2) is a semi-metallic layered transition metal dichalcogenide with a stable distorted 1T phase. The reduced symmetry of this system leads to in-plane anisotropy in various materials properties. We have systemically studied the in-plane anisotropy of Raman modes in few-layer and bulk WTe2 by angle-dependent and polarized Raman spectroscopy (ADPRS). Ten Raman modes are clearly resolved. Their intensities show periodic variation with sample rotating. We identify the symmetries of the detected modes by quantitatively analyzing the ADPRS results based on the symmetry selection rules. Material absorption effect on the phonon modes with high vibration frequencies is investigated by considering complex Raman tensor elements. We also provide a rapid and nondestructive method to identify the crystallographic orientation of WTe2. The crystallographic orientation is further confirmed by the quantitative atomic-resolution force image. Finally, we find that the atomic vibrational tendency and complexity of detected modes are also reflected in the shrinkage degree defined based on ADPRS, which is confirmed by corresponding density functional calculation. Our work provides a deep understanding of the interaction between WTe2 and light, which will benefit in future studies about the anisotropic physical properties of WTe2 and other in-plane anisotropic materials.
authors.affiliation: State Key Lab for Mesoscopic Physics and School of Physics, Peking University, Beijing, 100871, China.|Collaborative Innovation Center of Quantum Matter, Beijing, 100871, China.
authors.forename: Qingjun
authors.initials: Q
authors.lastname: Song
authors.affiliation: National Laboratory of Solid State Microstructures, College of Physics, Nanjing University, Nanjing, 210093, China.|Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China.
authors.forename: Xingchen
authors.initials: X
authors.lastname: Pan
authors.affiliation: National Laboratory of Solid State Microstructures, College of Physics, Nanjing University, Nanjing, 210093, China.|Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China.
authors.forename: Haifeng
authors.initials: H
authors.lastname: Wang
authors.affiliation: State Key Lab for Mesoscopic Physics and School of Physics, Peking University, Beijing, 100871, China.|Collaborative Innovation Center of Quantum Matter, Beijing, 100871, China.
authors.forename: Kun
authors.initials: K
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, 100083, China.
authors.forename: Qinghai
authors.initials: Q
authors.lastname: Tan
authors.affiliation: MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, Xi'an Jiaotong University, Xi'an, 710049, P. R. China.
authors.forename: Pan
authors.initials: P
authors.lastname: Li
authors.affiliation: State Key Lab for Mesoscopic Physics and School of Physics, Peking University, Beijing, 100871, China.|Collaborative Innovation Center of Quantum Matter, Beijing, 100871, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Wan
authors.affiliation: State Key Lab for Mesoscopic Physics and School of Physics, Peking University, Beijing, 100871, China.|Collaborative Innovation Center of Quantum Matter, Beijing, 100871, China.
authors.forename: Yilun
authors.initials: Y
authors.lastname: Wang
authors.affiliation: State Key Lab for Mesoscopic Physics and School of Physics, Peking University, Beijing, 100871, China.|Collaborative Innovation Center of Quantum Matter, Beijing, 100871, China.
authors.forename: Xiaolong
authors.initials: X
authors.lastname: Xu
authors.affiliation: State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, 100083, China.
authors.forename: Miaoling
authors.initials: M
authors.lastname: Lin
authors.affiliation: National Laboratory of Solid State Microstructures, College of Physics, Nanjing University, Nanjing, 210093, China.|Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China.
authors.forename: Xiangang
authors.initials: X
authors.lastname: Wan
authors.affiliation: National Laboratory of Solid State Microstructures, College of Physics, Nanjing University, Nanjing, 210093, China.|Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China.
authors.forename: Fengqi
authors.initials: F
authors.lastname: Song
authors.affiliation: State Key Lab for Mesoscopic Physics and School of Physics, Peking University, Beijing, 100871, China.|Collaborative Innovation Center of Quantum Matter, Beijing, 100871, China.
authors.forename: Lun
authors.initials: L
authors.lastname: Dai