Transport via double constrictions in integer and fractional topological insulators

TL;DR

This paper investigates the transport behavior of helical edge states in integer and fractional topological insulators with double constrictions, revealing Kondo physics and potential metal-insulator transitions influenced by tuning parameters.

Contribution

It introduces a detailed analysis of double constrictions in topological insulators, uncovering Kondo effects and phase transitions using renormalization group and duality methods.

Findings

Identification of Kondo behavior at resonance conditions.

Prediction of a metal-insulator transition at finite detuning.

Observation of two temperature scales affecting conductance.

Abstract

We study transport properties of the helical edge states of two-dimensional integer and fractional topological insulators via double constrictions. Such constrictions couple the upper and lower edges of the sample, and can be made and tuned by adding side gates to the system. Using renormalization group and duality mapping, we analyze phase diagrams and transport properties in each of these cases. Most interesting is the case of two constrictions tuned to resonance, where we obtain Kondo behavior, with a tunable Kondo temperature. Moving away from resonance gives the possibility of a metal-insulator transition at some finite detuning. For integer topological insulators, this physics is predicted to occur for realistic interaction strengths and gives a conductance $G$ with two temperature $T$ scales where the sign of $dG/dT$ changes; one being related to the Kondo temperature while the other is related to the detuning.