Spin current pumping in helical Luttinger liquids

TL;DR

This paper investigates how DC spin currents can be generated in quantum spin Hall systems using time-dependent tunneling, revealing interference effects that inform on edge state properties and electron interactions.

Contribution

It introduces a method to analyze spin current pumping in helical Luttinger liquids via interference patterns, linking observable oscillations to system parameters.

Findings

Spin-preserving and spin-flipping contributions show oscillations with frequency, interaction, and temperature.

Interference patterns reveal the helical nature of edge states.

Method allows extraction of electron-electron interaction strength.

Abstract

We study the DC spin current induced into an unbiased quantum spin Hall system through a two-point contacts setup with time dependent electron tunneling amplitudes. By means of two external gates, it is possible to drive a current with spin-preserving and spin-flipping contributions showing peculiar oscillations as a function of pumping frequency, electron-electron interaction and temperature. From its interference patterns as a function of the Fabry-Perot and Aharonov-Bohm phases, it is possible to extract information about the helical nature of the edge states and the intensity of the electron-electron interaction.