  Here we report the formation of type-A and type-B electronic junctions
without any structural discontinuity along a well-defined 1-nm-wide
one-dimensional electronic channel within a van der Waals layer. We employ
scanning tunneling microscopy and spectroscopy techniques to investigate the
atomic and electronic structure along peculiar domain walls formed on the
charge-density-wave phase of 1T-TaS2. We find distinct kinds of abrupt
electronic junctions with discontinuities of the band gap along the domain
walls, which do not have any structural kinks and defects. Our
density-functional calculations reveal a novel mechanism of the electronic
junction formation; they are formed by a kinked domain wall in the layer
underneath through substantial electronic interlayer coupling. This work
demonstrates that the interlayer electronic coupling can be an effective
control knob over several-nanometer-scale electronic property of
two-dimensional atomic monolayers.
