Raman Signatures of Broken Inversion Symmetry and In-Plane Anisotropy in Type-II Weyl Semimetal Candidate TaIrTe4

Yinan Liu; Qiangqiang Gu; Yu Peng; Shaomian Qi; Na Zhang; Yinong Zhang; Xiumei Ma; Rui Zhu; Lianming Tong; Ji Feng; Zheng Liu; Jian-Hao Chen

doi:10.1002/adma.201706402

Raman Signatures of Broken Inversion Symmetry and In-Plane Anisotropy in Type-II Weyl Semimetal Candidate TaIrTe₄

Adv Mater. 2018 Jun;30(25):e1706402. doi: 10.1002/adma.201706402. Epub 2018 May 7.

Authors

Yinan Liu¹, Qiangqiang Gu¹, Yu Peng², Shaomian Qi¹, Na Zhang³, Yinong Zhang¹, Xiumei Ma⁴, Rui Zhu⁴, Lianming Tong³, Ji Feng^{1

5

6}, Zheng Liu^{2

7}, Jian-Hao Chen^{1

6}

Affiliations

¹ International Center for Quantum Materials, School of Physics, Peking University, No. 5 Yiheyuan Road, Beijing, 100871, China.
² Centre for Programmed Materials, School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798, Singapore.
³ College of Chemistry and Molecular Engineering, Peking University, No. 5 Yiheyuan Road, Beijing, 100871, China.
⁴ Electron Microscopy Laboratory, School of Physics, Peking University, Beijing, 100871, China.
⁵ CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing, 100190, China.
⁶ Collaborative Innovation Center of Quantum Matter, Beijing, 100871, China.
⁷ NOVITAS, Nanoelectronics Centre of Excellence, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore, 639798, Singapore.

PMID: 29736942
DOI: 10.1002/adma.201706402

Abstract

The layered ternary compound TaIrTe₄ is an important candidate to host the recently predicted type-II Weyl fermions. However, a direct and definitive proof of the absence of inversion symmetry in this material, a prerequisite for the existence of Weyl Fermions, has so far remained evasive. Herein, an unambiguous identification of the broken inversion symmetry in TaIrTe₄ is established using angle-resolved polarized Raman spectroscopy. Combining with high-resolution transmission electron microscopy, an efficient and nondestructive recipe to determine the exact crystallographic orientation of TaIrTe₄ crystals is demonstrated. Such technique could be extended to the fast identification and characterization of other type-II Weyl fermions candidates. A surprisingly strong in-plane electrical anisotropy in TaIrTe₄ thin flakes is also revealed, up to 200% at 10 K, which is the strongest known electrical anisotropy for materials with comparable carrier density, notably in such good metals as copper and silver.

Keywords: 2D material; DFT calculations; Raman spectroscopy; in-plane anisotropy; type-II Weyl semimetal.