Quasiparticle interference of surface states in the type-II Weyl semimetal WTe2

Abstract

Topological Weyl semimetal (TWS) is a metal, where low energy excitations behave like Weyl fermions of high-energy physics. It was recently shown that due to the lower symmetry of condensed matter systems, they can realize two distinct types of Weyl fermions. The type-I Weyl fermion in a metal is formed by a linear crossing of two bands at a point in the crystalline momentum space -Brillouin zone (BZ). The second type TWSs host type-II Weyl points appearing at the touching points of electron and hole pockets, which is a result of tilted linear dispersion. The type-II TWS was predicted to exist in several compounds, including WTe 2 . Several ARPES studies of WTe 2 were reported so far, having contradictory conclusions on the topological nature of observed Fermi arcs. In this work, we report the results of spectroscopic imaging with a scanning tunneling microscope and first principle calculations, establishing clear quasiparticle interference features of the surface states of WTe 2 . Our work provides a strong evidence for surface state scattering.Although the surface Fermi arcs are clearly observed, it is still difficult to prove the existence of predicted Type-II Weyl points in the bulk.

Evidence of higher-order topology in multilayer WTe2 from Josephson coupling through anisotropic hinge states

“…Recently, it was proposed that bulk MoTe2 and WTe2 in Td structures are higher order topological insulators (HOTIs), and that large surface states arising from gapped fourfold Dirac surfaces would be present 20 . Their signatures were actually observed previously but not understood; large surface states not attributable to the Fermi arcs arising from the Weyl points were seen by ARPES and STM in bulk WTe2 and MoTe2 21,22 . In addition, WTe2 was proposed to have topologically protected conducting helical hinge states 20 , which would coexist with bulk conduction states and be difficult to resolve by transport measurements.…”

Synthesis of tungsten ditelluride thin films and highly crystalline nanobelts from pre-deposited reactants

“…Furthermore, it was the first material to be suggested as a potential type-II Weyl semimetal [20]. Since this prediction, there has been a number of experimental reports that have lent credence to this assertion [21,22].…”

“…Other works have examined WTe 2 for use in applications such as nanoscale electrical interconnects [23], electrocatalysis [24,25] and as an anode material for Na-ion batteries [26]. Additionally, WTe 2 has been touted as a promising candidate for large-gap quantum spin Hall insulators [5,21,22]. Lastly, through electrochemical investigations, the possibility of using WTe 2 as a catalyst for the hydrogen evolution reaction (HER) has been examined [24,[27][28][29][30].…”

Unconventional Charge–Spin Conversion in Weyl‐Semimetal WTe2

“…The WTe 2 has been experimentally verified to be a type‐II Weyl semimetal by observing the negative magnetoresistance [ 8,41 ] and the anomalous‐quantum oscillation [ 8 ] at low temperatures. However, the verification of WTe 2 to be a type‐II Weyl semimetal at room temperature is still under debate, [ 31,42,43 ] because the momentum difference for Weyl points (WPs) is beyond the resolution of ARPES measurement. [ 7,31,44 ] Hence, it is intriguing to check the temperature dependence of the signal and its relationship with the possible Weyl phase transition at a lower temperature.…”