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 have gathered a great deal of attention because of the quasiparticles inside them 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 STM and ARPES.

Recently temperature-dependent transport properties of MoTe2 are reported [3]. 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. 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] Q. L. Pei et al., Phys. Rev. B 96, 075132 (2017).