Partial heating between counter propagating quantum Hall edge channels

In contrast to clear unidirectional charge flow in quantum Hall edge channels, heat transport and equilibration remain veiled. Most of the previous works were concentrated on heating between co-propagating edge channels, where co-propagating charge and spin modes are formed by the Coulomb interaction [1]. Here, we investigate heating between counter propagating edge channels separated by a narrow surface gate of the width 0.1 $\mu$m, where the plasmon coupling forms counter-propagating dragging modes [2]. One edge channel is directly heated up by a quantum point contact at its half transmission, and energy spectrum of the other edge channel is evaluated by quantum dot thermometry. We observed partial heating in the spectrum, where a small fraction (1-5 percent) of electrons is highly excited over the original Fermi distribution, for an interaction length of 5-10 $\mu$m in the coupled channels. This can be understood by considering weak scattering process between the channels. The flow of this non-equilibrium distribution will be discussed with different configurations of heating and detecting channels in terms of the chirality and the dragging modes.\\[4pt] [1] H. le Sueur el al., PRL 105, 056803 (2010)\\[0pt] [2] H. Kamata et al., to be published. (cond-mat/1309.7471)