Spin current pumping in helical Luttinger liquids

We study parametric quantum pumping in a two-dimensional topological insulator bar in the presence of electron interactions described by a helical Luttinger liquid. The pumping current is generated by two point contacts whose tunneling amplitudes are modulated in time. The helical nature of the edge states of the system ensures the generation of a pumped spin current that is determined by interference effects related to spin-flipping or spin-preserving tunneling at the quantum point contacts and which can be controlled by all electrical means. We show that the period of oscillation and the position of the zeros of the spin current depend on the strength of the electron interactions, giving the opportunity to directly extract information about them when measured. © 2013 American Physical Society.