Quantum Transport Detected by Strong Proximity Interaction at a Graphene–WS₂ van der Waals Interface

Magnetotransport measurements demonstrate that graphene in a van der Waals heterostructure is a sensitive probe of quantum transport in an adjacent WS₂ layer via strong Coulomb interactions. We observe a large low-field magnetoresistance (≫ <i>e</i>²/<i>h</i>) and a −ln <i>T</i> temperature dependence of the resistance. In-plane magnetic field resistance indicates the origin is orbital and nonclassical. We demonstrate a strong electron–hole asymmetry in the mobility and coherence length of graphene demonstrating the presence of localized Coulomb interactions with ionized donors in the WS₂ substrate, which ultimately leads to screening as the Fermi level of graphene is tuned toward the conduction band of WS₂. This leads us to conclude that graphene couples to quantum localization processes in WS₂ via the Coulomb interaction and results in the observed signatures of quantum transport. Our results show that theoretical descriptions of the van der Waals interface should not ignore localized strong correlations

Creating a Stable Oxide at the Surface of Black Phosphorus

The stability of the surface of in situ cleaved black phosphorus crystals upon exposure to atmosphere is investigated with synchrotron-based photoelectron spectroscopy. After 2 days atmosphere exposure a stable subnanometer layer of primarily P₂O₅ forms at the surface. The work function increases by 0.1 eV from 3.9 eV for as-cleaved black phosphorus to 4.0 eV after formation of the 0.4 nm thick oxide, with phosphorus core levels shifting by <0.1 eV. The results indicate minimal charge transfer, suggesting that the oxide layer is suitable for passivation or as an interface layer for further dielectric deposition