Shot noise of the edge transport in the inverted band HgTe quantum wells

TL;DR

This study examines shot noise in disordered HgTe quantum wells with inverted bands, revealing multi-mode conduction rather than ideal helical edge transport, with noise characteristics indicating complex edge conduction mechanisms.

Contribution

It provides experimental evidence that disordered multi-mode conduction dominates edge transport in HgTe quantum wells, challenging the assumption of ideal helical edge states.

Findings

Edge resistance exceeds $h/e^2$ and is temperature-independent.

Shot noise Fano factor ranges from 0.1 to 0.3, below Poissonian.

Devices are shorter than the ballistic dephasing length, excluding ideal 1D helical transport.

Abstract

We investigate the current noise in HgTe-based quantum wells with an inverted band structure in the regime of disordered edge transport. Consistent with previous experiments, the edge resistance strongly exceeds $h/e^2$ and weakly depends on the temperature. The shot noise is well below the Poissonian value and characterized by the Fano factor with gate voltage and sample to sample variations in the range $0.1<F<0.3$. Given the fact that our devices are shorter than the most pessimistic estimate of the ballistic dephasing length, these observations exclude the possibility of one-dimensional helical edge transport. Instead, we suggest that a disordered multi-mode conduction is responsible for the edge transport in our experiment.