Impact of electron heating on the equilibration between quantum Hall edge channels

TL;DR

This study investigates how electron heating affects the equilibration process between quantum Hall edge channels, revealing that junction length influences threshold voltage for photon emission due to electron heating effects.

Contribution

It introduces a tunable quantum Hall circuit to study length-dependent electron heating effects on edge channel equilibration and photon emission thresholds.

Findings

Threshold voltage for photon emission depends on junction length.

Electron heating is identified as the main factor reducing the threshold.

Spatially resolved measurements support the heating model.

Abstract

When two separately contacted quantum Hall (QH) edge channels are brought into interaction, they can equilibrate their imbalance via scattering processes. In the present work we use a tunable QH circuit to implement a junction between co-propagating edge channels whose length can be controlled with continuity. Such a variable device allows us to investigate how current-voltage characteristics evolve when the junction length d is changed. Recent experiments with fixed geometry reported a significant reduction of the threshold voltage for the onset of photon emission, whose origin is still under debate. Our spatially resolved measurements reveal that this threshold shift depends on the junction length. We discuss this unexpected result on the basis of a model which demonstrates that a heating of electrons is the dominant process responsible for the observed reduction of the threshold voltage.