Epitaxially defined Luttinger liquids on MoS$_2$ bicrystals

A mirror twin boundary (MTB) in a transition metal dichalcogenide (TMD) monolayer can host one-dimensional electron liquid of a topological nature with tunable interactions. Unfortunately, the electrical characterization of such boundaries has been challenging due to the paucity of samples with large enough size and high quality. Here, we report an epitaxial growth of monolayer molybdenum disulfide (MoS$_2$) bicrystals with well-isolated MTBs that are tens of micrometers long. Conductance measurements of these MTBs exhibit power-law behaviors as a function of temperature and bias voltage up to room temperature, consistent with electrons tunneling into a Luttinger liquid. Transport measurements of two distinct types of MTBs reveal the critical role of the atomic-scale defects. This study demonstrates that MTBs in TMD monolayers provide an exciting new platform for studying the interplay between electronic interactions and topology.