Abstract
Topological Weyl semimetal (TWS), a new state of quantum matter, has sparked enormous research interest recently. Possessing unique Weyl fermions in the bulk and Fermi arcs on the surface, TWSs offer a rare platform for realizing many exotic physical phenomena. TWSs can be classified into type-I that respect Lorentz symmetry and type-II that do not. Here, we directly visualize the electronic structure of MoTe2, a recently proposed type-II TWS. Using angle-resolved photoemission spectroscopy (ARPES), we unravel the unique surface Fermi arcs, in good agreement with our ab initio calculations that have nontrivial topological nature. Our work not only leads to new understandings of the unusual properties discovered in this family of compounds, but also allows for the further exploration of exotic properties and practical applications of type-II TWSs, as well as the interplay between superconductivity (MoTe2 was discovered to be superconducting recently) and their topological order.
Highlights
Topological Weyl semimetal (TWS), a new state of quantum matter, has sparked enormous research interest recently
In a TWS, low-energy electronic excitations form composite Weyl fermions dispersing linearly along all the three momentum directions across the Weyl points (WPs)[7,8,9,10] that always appear in pairs with opposite chirality
The TWSs can be further classified into two types by Fermiology and whether the Lorentz symmetry is respected: type-I TWS that hosts point-like bulk Fermi surfaces (FSs) formed solely by WPs that approximately respect the Lorentz symmetry[4,5,6]; and type-II TWS that breaks the Lorentz symmetry and harbours finite electron density of states at the Fermi energy
Summary
Topological Weyl semimetal (TWS), a new state of quantum matter, has sparked enormous research interest recently. The exotic bulk and surface electronic structures provide an ideal platform for many novel physical phenomena, such as negative magnetoresistance, anomalous quantum Hall effect and chiral magnetic effects[11,12,13,14,15,16,17,18,19,20]. With less WPs and nonvanishing electronic density of states at the Fermi surface, type-II TWSs in TMD compounds are expected to show very different properties from the type-I TWSs, such as anisotropic chiral anomaly depending on the current directions, a novel anomalous Hall effect[24]. The discovery of the TWS phase in MoTe2 could help understand the puzzling physical properties in the orthorhombic phase of TMDs recently observed[29], and provide a more feasible material platform for the future applications of TWSs because of their layered structures. With the recent discovery of superconductivity in MoTe2 (ref. 25), it even provides an ideal platform for the study of interplays between superconductivity and the nontrivial topological order
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