Effective tunneling processes in an interferometer of helical edge states with an antidot

BRUNO RIZZO; ALBERTO CAMJAYI; L. ARRACHEA

Conferencia; 27th International Conference on Low Temperature Physics; 2014

Recent experiments in quantum wells of the two-dimensional topological insulator HgTe demonstrated a dissipationless charge transport through its helical edge states (HES). Due to the time reversal symmetry that holds in this material, the edge states come in Kramer?s pairs, through which the electrons move with a defined spin associated with the direction of propagation.The nature of the electron propagation in HES along with the topological protection against backscattering, make these materials very appealing to be employed for spintronics and quantumcomputation. This motivates the study of configurations of helical interferometers in setups including voltages and constrictions akin to those fabricated with quantum Hall edge states. So far, most of the studies were based on scattering at quantum point contacts connecting two HES, while the effect of a wide tunnelling contact was also recently analyzed. Quite generally, the (local) time-reversal invariance only allows for the direct scattering between edge states situated at different sides of the sample, while the direct (back) scattering within the same Kramer?s pair is forbidden even in the presence of a constriction. Therefore, the scattering at the point contact is characterized by two parameters, one describing a spin-preserving tunneling and one describing a spin-flip tunneling between two Kramer?s pairs. However it is still unclear whether these effects are present in real setups.