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1D metallic states at 2D transition metal dichalcogenide semiconductor heterojunctions

Two-dimensional (2D) lateral heterojunctions of transition metal dichalcogenides (TMDCs) have become a reality in recent years. Semiconducting TMDC layers in their common H -structure have a nonzero in-plane electric polarization, which is a topological invariant. We show by means of first-principles calculations that lateral 2D heterojunctions between TMDCs with a different polarization generate one-dimensional (1D) metallic states at the junction, even in cases where the different materials are joined epitaxially. The metallicity does not depend upon structural details, and is explained from the change in topological invariant at the junction. Nevertheless, these 1D metals are susceptible to 1D instabilities, such as charge- and spin-density waves, making 2D TMDC heterojunctions ideal systems for studying 1D physics.