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Two-dimensional crystals of semimetallic van der Waals materials hold much potential for the realization of novel phases, as exemplified by the recent discoveries of a polar metal in few layer 1T-WTe$_2$ and of a quantum spin Hall state in monolayers of the same material. Understanding these phases is particularly challenging because little is known from experiment about the momentum space electronic structure of ultrathin crystals. Here, we report direct electronic structure measurements of exfoliated mono-, bi-, and few-layer 1T-WTe$_2$ by laser-based micro-focus angle resolved photoemission. This is achieved by encapsulating with monolayer graphene a flake of WTe$_2$ comprising regions of different thickness. Our data support the recent identification of a quantum spin Hall state in monolayer 1T-WTe$_2$ and reveal strong signatures of the broken inversion symmetry in the bilayer. We finally discuss the sensitivity of encapsulated samples to contaminants following exposure to ambient atmosphere.
Laser-based angle-resolved photoemission spectroscopy (ARPES) and two-photon photoemission spectroscopy (2PPES) are employed to study the valence electronic structure of the Weyl semimetal candidate Td-WTe$_2$ along two high symmetry directions and f
We study the second-order Raman process of mono- and few-layer MoTe$_2$, by combining {em ab initio} density functional perturbation calculations with experimental Raman spectroscopy using 532, 633 and 785 nm excitation lasers. The calculated electro
We report electron transport studies in an encapsulated few-layer WTe$_2$ at low temperatures and high magnetic fields. The magnetoconductance reveals a temperature-induced crossover between weak antilocalization (WAL) and weak localization (WL) in q
Charge-density-waves (CDW) which occur mainly in low-dimensional systems have a macroscopic wave function similar to superfluids and superconductors. Kosterlitz-Thouless (KT) transition is observed in superfluids and superconductors, but the presence
Room temperature two-dimensional (2D) ferromagnetism is highly desired in practical spintronics applications. Recently, 1T phase CrTe2 (1T-CrTe2) nanosheets with five and thicker layers have been successfully synthesized, which all exhibit the proper