Imaging topologically protected transport with quantum degenerate gases

Ultracold and quantum degenerate gases held near conductive surfaces can serve as sensitive, high-resolution, and wide-area probes of electronic current flow. Previous work has imaged transport around grain boundaries in a gold wire by using ultracold and Bose-Einstein condensed atoms held microns from the surface with an atom-chip trap. We show that atom-chip microscopy may be applied to useful purpose in the context of materials exhibiting topologically protected surface transport. Current flow through lithographically tailored surface defects in topological insulators (TI), both idealized and with the band structure and conductivity typical of Bi ₂Se ₃, is numerically calculated. We propose that imaging current flow patterns enables the differentiation of an ideal TI from one with a finite bulk-to-surface conductivity ratio, and specifically, that the determination of this ratio may be possible by imaging transport around trenches etched into the TI's surface.