Colloquium
Department of Physics, NCU
Temperature-Dependent Electronic Structures of TMD Weyl Semimetals
Prof. Chun-Liang Lin(林俊良)
Department of Electrophysics, National Yang Ming Chiao Tung University
Date 2021.12.07 (Tue)
Place S4-625
Time 14:00-16:00
Abstract:
Transition metal dichalcogenides (TMDs) are layered materials with chemical compositions described as MX2. Here, M represents an element of transition metals such as Nb, Mo, and W, and X a chalcogen atom such as S, Se, and Te. Most TMDs are semiconducting with valley degrees of freedom to generate an application in information processing. On the other hand, MoTe2 and WTe2 are TMDs and have been proposed as candidates for Weyl semimetals [1, 2]. Both of them have gathered a great deal of attention because of the quasiparticles on their crystal surface 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 Angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy (STM) based quasiparticles interference (QPI).
Recently temperature-dependent transport properties of both WTe2 and MoTe2 are reported [3, 4]. Therefore, it is urgent to reveal the temperature-dependent electronic structures of these TMD Weyl Semimetals. By using STM and STM-QPI, both structure and electronic structures of MoTe2 and WTe2 are clearly revealed. Surprisingly, huge variations are found in between the results measured at 5K and 77K. For WTe2, slight shifts of both two Fermi arc surface states (SS1 and SS2) and Weyl points (WPs) are obseverd. Much large variations are found in the results of MoTe2. The current work provides valuable insights into the temperature-dependent properties of TMD semimetals.
[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).