Quantum point contact potential curvature under correlated disorder potentials

We theoretically investigate the curvature of the confinement potential in quantum point contacts (QPCs) under a background disorder potential with Gaussian correlation functions using a noninteracting one-dimensional tight-binding model. The curvature of the potential is evaluated from the gate voltage dependence of the conductance, and the statistical average of the fitting curvature is calculated. The fitting curvature is insensitive to the original QPC confinement curvature when the characteristic length of the QPC potential is larger than the characteristic length of the disorder. In addition, the fitting curvature can be enhanced as the QPC curvature is decreased. Accidental double barrier potential formation on the top of the QPC induces enhancement of the fitting curvature. Finite-temperature effects under the disorder potential are also discussed. Similar results hold in a two-dimensional QPC tight-binding model.