Laboratory for Topological Quantum Matter and Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey 08544, USA.
The Institute for Solid State Physics (ISSP), University of Tokyo, Kashiwa-no-ha, Kashiwa, Chiba 277-8581, Japan.
Nat Commun. 2016 Dec 5;7:13643. doi: 10.1038/ncomms13643.
The recent discovery of a Weyl semimetal in TaAs offers the first Weyl fermion observed in nature and dramatically broadens the classification of topological phases. However, in TaAs it has proven challenging to study the rich transport phenomena arising from emergent Weyl fermions. The series MoWTe are inversion-breaking, layered, tunable semimetals already under study as a promising platform for new electronics and recently proposed to host Type II, or strongly Lorentz-violating, Weyl fermions. Here we report the discovery of a Weyl semimetal in MoWTe at x=25%. We use pump-probe angle-resolved photoemission spectroscopy (pump-probe ARPES) to directly observe a topological Fermi arc above the Fermi level, demonstrating a Weyl semimetal. The excellent agreement with calculation suggests that MoWTe is a Type II Weyl semimetal. We also find that certain Weyl points are at the Fermi level, making MoWTe a promising platform for transport and optics experiments on Weyl semimetals.
在 TaAs 中发现的 Weyl 半金属首次提供了在自然界中观察到的 Weyl 费米子，极大地拓宽了拓扑相的分类。然而，在 TaAs 中，研究新兴 Weyl 费米子引起的丰富输运现象一直具有挑战性。MoWTe 系列是具有非中心对称、层状、可调的半金属，已经作为新电子学的一个有前途的平台进行研究，并最近被提议为 II 型，或强烈违反洛伦兹不变性的 Weyl 费米子的宿主。在这里，我们报告了在 MoWTe 中 x=25%处发现的 Weyl 半金属。我们使用泵浦探测角分辨光电子能谱（pump-probe ARPES）直接观察到费米能级上方的拓扑费米弧，证明了 Weyl 半金属的存在。与计算的出色一致性表明，MoWTe 是一种 II 型 Weyl 半金属。我们还发现某些 Weyl 点位于费米能级，这使得 MoWTe 成为研究 Weyl 半金属输运和光学实验的一个很有前途的平台。
