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Influence of e-e scattering on the temperature dependence of the resistance of a classical ballistic point contact in a two-dimensional electron system

We experimentally investigate the temperature (T) dependence of the resistance of a classical ballistic point contact (PC) in a two-dimensional electron system (2DES). The split-gate PC is realized in a high-quality AlGaAs/GaAs heterostructure. The PC resistance is found to drop by more than 10% as T is raised from 0.5 K to 4.2 K. In the absence of a magnetic field, the T dependence is roughly linear below 2 K and tends to saturate at higher T. Perpendicular magnetic fields on the order of a few 10 mT suppress the T-dependent contribution dR. This effect is more pronounced at lower temperatures, causing a crossover to a nearly parabolic T dependence in a magnetic field. The normalized magnetic field dependencies dR(B) permit an empiric single parameter scaling in a wide range of PC gate voltages. These observations give strong evidence for the influence of electron-electron (e-e) scattering on the resistance of ballistic PCs. Our results are in qualitative agreement with a recent theory of the e-e scattering based T dependence of the conductance of classical ballistic PCs [ Phys. Rev. Lett. 101 216807 (2008) and Phys. Rev. B 81 125316 (2010)].