Imaging effects of interactions in semiconducting nanowires coupled to quantum dots.*

Electrons confined to one dimension exhibit various counter-intuitive phenomena such as charge fractionalization, spin-charge separation, and Majorana end modes induced at nanowires rendered topologically superconducting. We perform spectroscopic mappings of the electronic states in semiconducting InAs nanowires through scanning tunneling microscopy. We identify an indirect charging mechanism where in-gap resonances act as a switch for the conductance of the one-dimensional states, resulting in negative differential conductance. The interaction between the resonances and the continuum is mediated by quantum dots that naturally form both in the gold droplets used to catalyze the nanowire growth as well as in aluminum droplets epitaxially grown on the nanowire side facets. The detection of this phenomena is enabled by maintaining the MBE grown nanowires under ultra-high vacuum. This allows us to visualize the electronic spectrum through local spectroscopy. This technology paves the way for the study of additional exotic phenomena in one dimensional nanowires such as induced topological superconductivity and Majorana end modes therein.