Fermi arc electronic structure and Chern numbers in the type-II Weyl semimetal candidate MoxW1-xTe2

It has recently been proposed that electronic band structures in crystals can give rise to a previously overlooked type of Weyl fermion, which violates Lorentz invariance and, consequently, is forbidden in particle physics. It was further predicted that MoxW1-xTe2 may realize such a type-II Weyl fermion. Here, we first show theoretically that it is crucial to access the band structure above the Fermi level epsilon(F) to show a Weyl semimetal in MoxW1-xTe2. Then, we study MoxW1-xTe2 by pump-probe ARPES and we directly access the band structure > 0.2 eV above epsilon(F) in experiment. By comparing our results with ab initio calculations, we conclude that we directly observe the surface state containing the topological Fermi arc. We propose that a future study of MoxW1-xTe2 by pump-probe ARPES may directly pinpoint the Fermi arc. Our work sets the stage for the experimental discovery of the first type-II Weyl semimetal in MoxW1-xTe2.

最近有人提出，晶体中的电子能带结构可能会产生一种先前被忽视的外尔费米子类型，它违反洛伦兹不变性，因此在粒子物理学中是被禁止的。进一步预测MoₓW₁₋ₓTe₂可能会实现这种第二类外尔费米子。在此，我们首先从理论上表明，获取费米能级ε(F)之上的能带结构对于在MoₓW₁₋ₓTe₂中展示外尔半金属至关重要。然后，我们通过泵浦 - 探测角分辨光电子能谱（ARPES）研究MoₓW₁₋ₓTe₂，并在实验中直接获取了费米能级之上>0.2电子伏特的能带结构。通过将我们的结果与从头算计算进行比较，我们得出结论：我们直接观测到了包含拓扑费米弧的表面态。我们提出，未来通过泵浦 - 探测角分辨光电子能谱对MoₓW₁₋ₓTe₂进行研究可能会直接确定费米弧。我们的工作为在MoₓW₁₋ₓTe₂中实验发现第一种第二类外尔半金属奠定了基础。