2D quantum oscillations in the normal state of a superconducting oxide heterostructure

We present a novel system showing 2D superconductivity and 2D Shubnikov-de Haas (SdH) oscillations, realized in a SrTiO$_{3}$ heterostructure using the delta-doping technique [1]. As the thickness of the dopant layer (1 at.{\%} Nb:SrTiO$_{3})$ inserted between insulating SrTiO$_{3}$ layers decreases, a 3D to 2D crossover in the superconducting state is observed from the anisotropy and temperature dependence of the upper critical field. In the normal state, the thinnest sample (5.5 nm) shows SdH oscillations that scale with the perpendicular magnetic field. These results demonstrate a new possibility to explore the interplay of quantum transport and superconductivity. \\[4pt] [1] Y. Kozuka \textit{et al.}, \textit{Nature}, in press.