Long-range electronic reconstruction to a $d_{xz,yz}$-dominated Fermi   surface below the LaAlO$_3$/SrTiO$_3$ interface
  Low dimensionality, broken symmetry and easily-modulated carrier concentrations provoke novel electronic phase emergence at oxide interfaces. However, the spatial extent of such reconstructions - i.e. the interfacial "depth" - remains unclear. Examining LaAlO$_3$/SrTiO$_3$ heterostructures at previously unexplored carrier densities $n_{2D}\geq6.9\times10^{14}$ cm$^{-2}$, we observe a Shubnikov-de Haas effect for small in-plane fields, characteristic of an anisotropic 3D Fermi surface with preferential $d_{xz,yz}$ orbital occupancy extending over at least 100~nm perpendicular to the interface. Quantum oscillations from the 3D Fermi surface of bulk doped SrTiO$_3$ emerge simultaneously at higher $n_{2D}$. We distinguish three areas in doped perovskite heterostructures: narrow ($<20$ nm) 2D interfaces housing superconductivity and/or other emergent phases, electronically isotropic regions far ($>120$ nm) from the interface and new intermediate zones where interfacial proximity renormalises the electronic structure relative to the bulk. 
A.P. Petrovi\'c, A. Par\'e, T.R. Paudel, K. Lee, S. Holmes, C.H.W.   Barnes, A. David, T. Wu, E.Y. Tsymbal and C. Panagopoulos
cond-mat.str-el cond-mat.mtrl-sci