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

When two separately contacted quantum Hall (QH) edge channels are brought into interaction, they can equilibrate their imbalance via scattering processes. In this work, we use a tunable QH circuit to implement a junction between copropagating edge channels, the length of which 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, the origin of which 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 that demonstrates that a heating of electrons is the dominant process responsible for the observed reduction of the threshold voltage.