  Helical Luttinger liquids, appearing at the edge of two-dimensional
topological insulators, represent a new paradigm of one-dimensional systems,
where peculiar quantum phenomena can be investigated. Motivated by recent
experiments on charge fractionalization, we propose a setup based on helical
Luttinger liquids that allows to time-resolve, in addition to charge
fractionalization, also spin-charge separation and pure spin fractionalization.
This is due to the combined presence of spin-momentum locking and interactions.
We show that electric time-resolved measurements can reveal both charge and
spin properties, avoiding the need of magnetic materials. Although challenging,
the proposed setup could be achieved with nowadays technologies, promoting
helical liquids as interesting playgrounds to explore the effects of
interactions in one dimension.
