Temperature-Dependent Electronic Structures of TMD Weyl Semimetals

Hsiang-I Huang¹, Naoya Kawakami¹, Ryuichi Arafune², Noriaki Takagi³, Chun-Liang Lin^1*

¹Department of Electrophysics, National Chiao Tung University, Hsinchu, Taiwan
²International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Ibaraki, Japan
³Graduate School of Human and Environmental Studies, Kyoto University, Kyoto, Japan

* Presenter:Chun-Liang Lin, email:clin@nctu.edu.tw

Transition metal dichalcogenides (TMDs) are layered materials with chemical compositions described as MX₂. Here, M represents an element of transition metals and X represents a chalcogen atom. Most TMDs are semiconducting with valley degrees of freedom to generate an application in information processing. On the other hand, MoTe₂ and WTe₂ are semimetallic and have been proposed as candidates for Weyl semimetals [1, 2]. Both have gathered a great deal of attention because the quasiparticles behave as massless chiral fermions −Weyl fermions. One of the unique characteristics of Weyl semimetals is the emergence of a topologically protected surface state called Fermi arc, which can be observed by scanning tunneling microscopy (STM) and angle-resolved angle-resolved photoemission spectroscopy (ARPES).
Recently temperature-dependent transport properties of both WTe₂ [3] and MoTe₂ [4] are reported. Therefore, it is urgent to reveal the temperature-dependent electronic structures of these Weyl Semimetals. By using STM and STM-QPI, both geometric and electronic structures of MoTe₂ and WTe₂ are clearly revealed. Surprisingly, huge variations are found in between the STM-QPI results measured at 5K and 77K. Our results may provide information to explain the temperature-dependent transport properties.
Reference:
[1] C. L. Lin et al., J. Phys.: Condens. Matter 32, 243001(2020). [2] C. L. Lin et al., ACS Nano 11, 11459 (2017). [3] L. R. Thoutam et al., Phys. Rev. Lett. 115, 046602 (2015). [4] Q. L. Pei et al., Phys. Rev. B 96, 075132 (2017).

Keywords: Weyl semimetals, Temperature-Dependent Properties, Scanning Tunneling Microscopy, Quasiparticle Interferece , Transition metal dichalcogenides