Abstract
We image equilibrium and non-equilibrium transport through a two-dimensional electronic cavity using scanning gate microscopy (SGM). Injecting electrons into the cavity through a quantum point contact close to equilibrium, we raster-scan a weakly invasive tip above the cavity regions and measure the modulated conductance through the cavity. Varying the electron injection energy between $\pm$ 2 meV, we observe that conductance minima turn into maxima beyond the energy threshold of $\pm$ 0.6 meV. This observation bears similarity to previous measurements by Jura et al. [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.
Highlights
Electron-electron (e-e) interactions and their role in electron transport are a topic of continuing interest in mesoscopic physics
We observe a minimum-to-maximum transition as a function of the source-drain bias Vsd,dc in the differential conductance modulation caused by the tip-induced potential
Our measurements show that gentle electron deflection due to a tip-induced potential below the Fermi energy [17] is sufficient to observe this transition
Summary
Electron-electron (e-e) interactions and their role in electron transport are a topic of continuing interest in mesoscopic physics. Raster scanning a locally depleting scanning gate tip above the open electron gas downstream of the injection point, the authors observed a contrast inversion of the branched electron flow signal at elevated source-drain bias voltages They interpreted this contrast inversion as a manifestation of e-e scattering in the electron gas. We recently found a method to significantly enhance the sensitivity at nondepleting voltages (weakly invasive regime) [17], reducing the influence of the tip on the unperturbed system This method utilizes a gate defined, open cavity structure [18,19,20], which concentrates the scattering density of states behind the quantum point contact and thereby enables scanning gate experiments at strongly reduced voltages applied to the scanning gate. Our finding may help unravel the microscopic details of this effect by theoretical means beyond the explanation given in Ref. [13]
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