Topological Appearances between Two Type-II Weyl Semimetals

Topology in abstract mathematics has revolutionized our conventional understanding of condensed matter physics, resulting in the emergence of exotic quantum phases such as topological insulators (TIs). Current realizations of the Weyl semimetals (WSMs) leads us to futher study the topological phases of matter beyond TIs. WSMs have gathered great attentions because the quasiparticles in WSMs behave as Weyl fermions, massless chiral fermions. WSMs are classified into Type I and II, according to the topology of the Weyl point, where the electron and hole pockets touch each other. Quasiparticle interference (QPI) study with STM has shown the evidence that a T_d phase Tungsten Ditelluride (WTe₂) is type-II WSM^{<span style="font-size:10.8333px">1)</span>}, agreeing with the prior theoretical predictions. A similar measurement has also been performed to a T_d phase Molybdenum Ditelluride (MoTe₂)²⁾. The difference in the topological appearance (i.e. the positions of the Weyl points and the Fermi arc surface states) of MoTe₂ from that of WTe₂ is clearly revealed.
¹⁾ C. –L. Lin et al. ACS Nano 11 11459 (2017)
²⁾ C. –L. Lin et al. J. Phys.: Condens. Matter 30 105703 (2018)