  When an electron with well-defined momentum tunnels into a nonchiral
Luttinger liquid, it breaks up into two separate wave packets that carry
fractional charges and move in opposite directions. A direct observation of
this phenomenon has proven elusive, mainly due to single-particle and plasmon
backscattering caused by measurement probes. This paper theoretically
introduces two topological insulator devices that are naturally suited for
detecting fractional charges and their velocities directly and in a noninvasive
fashion.
