Levitons in helical liquids with Rashba spin-orbit coupling probed by a superconducting contact

TL;DR

This paper investigates how Lorentzian voltage pulses generate minimal charge excitations in helical edge states of topological insulators with Rashba spin-orbit coupling, using a superconducting contact as a quantum beam splitter to analyze charge noise and quantum interference effects.

Contribution

It demonstrates that Lorentzian pulses produce minimal excitations in helical liquids with Rashba coupling and proposes a novel electron quantum optics setup with a superconducting contact.

Findings

Lorentzian pulses are minimal excitations even with Rashba spin-orbit interaction.

Charge noise analysis reveals a non-zero dip at zero delay in Hong-Ou-Mandel experiments.

Superconducting contact acts as an effective beamsplitter for helical edge states.

Abstract

We consider transport properties of a single edge of a two-dimensional topological insulators, in presence of Rashba spin-orbit coupling, driven by two external time-dependent voltages and connected to a thin superconductor. We focus on the case of a train of Lorentzian-shaped pulses, which are known to generate coherent single-electron excitations in two-dimensional electron gas, and prove that they are minimal excitations for charge transport also in helical edge states, even in the presence of spin-orbit interaction. Importantly, these properties of Lorentzian-shaped pulses can be tested computing charge noise generated by the scattering of particles at the thin superconductor. This represents a novel setup where electron quantum optics experiments with helical states can be implemented, with the superconducting contact as an effective beamsplitter. By elaborating on this configuration, we also evaluate charge noise in a collisional Hong-Ou-Mandel configuration, showing that, due to the peculiar effects induced by Rashba interaction, a non-vanishing dip at zero delay appears.