Negative charging energy in LaAlO${}_3$/SrTiO${}_3$ quantum dots induced by SrTiO${}_3$ polarization

We propose a microscopic mechanism for the negative charging energy in LaAlO${}_3$/SrTiO${}_3$ quantum dots, arising from the electrostatic image charge associated with the paraelectric response of SrTiO${}_3$. Using a self-consistent configuration-interaction approach that accounts for both Coulomb repulsion and image-charge interactions, we find a robust regime of electron pairing whose strength is tunable through the confinement potential and the effective image-charge distance, set by the thickness of the interfacial two-dimensional electron gas. Our results establish dielectric image-charge effects as a route to controllable electron pairing in oxide quantum dots and other materials with a strong dielectric response.