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.

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We report the experimental investigation of transport through bilayer graphene (BLG)/chromium trihalide (CrX3; X=Cl, Br, I) van der Waals interfaces. In all cases, a large charge transfer from BLG to CrX3 takes place (reaching densities in excess of 10 13 cm −2 ), and generates an electric field perpendicular to the interface that opens a band gap in BLG. We determine the gap from the activation energy of the conductivity and find excellent agreement with the latest theory accounting for the contribution of the sigma bands to the BLG dielectric susceptibility. We further show that for BLG/CrCl3 and BLG/CrB3 the band gap can be extracted from the gate voltage dependence of the low-temperature conductivity, and use this finding to refine the gap dependence on magnetic field. Our results allow a quantitative comparison of the electronic properties of BLG with theoretical predictions and indicate the presence of correlations in electrons occupying CrX3 conduction band.