Reprint of : Transient dynamics of spin-polarized injection in helical Luttinger liquids

• We study injection into the edge states of two-dimensional topological insulators.
• We model the system as a inhomogeneus helical Luttinger liquid.
• We find that signatures of fractionalization emerge in the transient regime only.
• We show that the setup can be experimentally feasible.

We analyze the time evolution of spin-polarized electron wave packets injected into the edge states of a two-dimensional topological insulator. In the presence of electron interactions, the system is described as a helical Luttinger liquid and injected electrons fractionalize. However, because of the presence of metallic detectors, no evidences of fractionalization are encoded in dc measurements, and in this regime the system does not show deviations from its non-interacting behavior. Nevertheless, we show that the helical Luttinger liquid nature emerges in the transient dynamics, where signatures of charge/spin fractionalization can be clearly identified.