Characterization of helical Luttinger liquids in microwave stepped-impedance edge resonators

TL;DR

This paper introduces simple microwave edge resonator geometries to quantify Coulomb interactions in quantum spin Hall edge states, enabling high-frequency measurements that reveal interaction effects on plasmon modes.

Contribution

It proposes novel resonator geometries and a transmission line approach to measure Coulomb interactions in helical Luttinger liquids.

Findings

Resonator geometries effectively characterize Coulomb interactions.

High-frequency measurements reveal renormalized plasmon velocities.

Impedance mismatch enhances measurement sensitivity.

Abstract

Coulomb interaction has important consequences on the physics of quantum spin Hall edge states, weakening the topological protection via two-particle scattering and renormalizing both the velocity and charge of collective plasmon modes compared to that of free electrons. Despite these effects, interactions remain difficult to quantify. We propose here simple and robust edge resonator geometries to characterize Coulomb interaction by means of high-frequency measurements. They rely on a transmission line approach, and take advantage of the impedance mismatch between the edge states and their microwave environment.