Doping a Mott insulator at the lateral junctions of single layer 1H-1T NbSe₂

At the single layer limit, transition metal dichalcogenides can adopt a variety of structural polymorphs with significantly different electronic properties. Here we report the selective growth of single layer 1T- and 1H-NbSe₂ on epitaxial graphene/SiC substrates by molecular beam epitaxy. Using a combination of scanning tunneling microscopy/spectroscopy and angle-resolved photoemission spectroscopy, we show that the 1H-NbSe₂ is metallic and exhibits a 3 by 3 charge density wave (CDW) at below 20K, while 1T-NbSe₂ is a Mott-insulator exhibiting a root 13 by root 13 CDW at room temperature. Furthermore, at the 1H-1T lateral junction, we observe a one-dimensional channel that is characterized by a V-shaped gap in tunneling spectroscopy. The spectra can be fitted by power law, similar to other substitutionally doped Mott insulators. Those finding suggests that lateral heterojunctions of different transition metal dichalcogenide polymorphs present an opportunity to engineer new quantum phases with emergent properties.