# Edge States in Lateral p-n Junctions in Inverted Band HgTe Quantum Wells

## TL;DR

This paper explores lateral p-n junctions in inverted band HgTe quantum wells, examining ballistic edge state transport through resistance and noise measurements, and discusses the challenges in conclusively identifying helical edge states.

## Contribution

It presents experimental investigation of transport in HgTe quantum wells with inverted bands, highlighting the potential of noise measurements to probe helical edge states in topological insulators.

## Key findings

- Resistances close to $h/2e^2$, indicating ballistic edge transport.
- Linear current-voltage characteristics consistent with edge conduction.
- Shot noise data suggestive but not conclusive of helical edge states.

## Abstract

We investigate lateral p-n junctions, electrostatically defined in 14 nm-wide HgTe-based quantum wells (QWs) with inverted band structure. The p-n junctions resistances are close to $h/2e^2$, consistent with some previous experiments on 8-10 nm QWs, and the current-voltage characteristics are highly linear, indicating the transport via ballistic helical edge states. Shot noise measurements are performed in order to further verify the underlying transport mechanism. We discuss the role of unknown inelastic relaxation rates in the leads and in the edge channels for the correct interpretation of the noise data. Although the interpretation in favor of the helical edge states seems more consistent, a definite conclusion can not be drawn based on the present experiment. Our approach looks promising for the study of short quasi-ballistic edges in topological insulators (TIs) in suitable geometry.