Local signatures of electron-electron scattering in an electronic cavity

We image equilibrium and nonequilibrium transport through a two-dimensional electronic cavity using scanning gate microscopy. Injecting electrons into the cavity through a quantum point contact close to equilibrium, we raster scan a weakly invasive tip above the cavity region and measure the modulated conductance through the cavity. Varying the electron injection energy between +/- 2meV, we observe that conductance minima turn into maxima beyond an energy threshold of +/- 0.6meV. This observation bears similarity to previous measurements by Jura et al. [Phys. Rev. B 82, 155328 (2010)], who used a strongly invasive tip potential to study electron injection into an open two-dimensional electron gas. This resemblance suggests a similar microscopic origin based on electron-electron interactions.