Publisher Correction: Direct imaging of the electron liquid at oxide interfaces

In the version of this Letter originally published, in two instances in Fig. 1 the layers in the cross-sectional view of the (001) interface were incorrectly labelled: in Fig. 1b SrO⁺ should have read SrO⁰; in Fig. 1c LaO⁺, AlO₂^-, LaO⁺, TiO₂⁰, SrO⁺, TiO₂⁰ should have read LaO₃^3-, Al³⁺, LaO₃^3-, Ti⁴⁺, SrO₃^4-, Ti⁴⁺. In Fig. 3c the upper-right equation read -σ_s = -e/2a² but should have read -σ_s = e/2a² and in Fig. 3f the lower-right equation read -σ_s = -e/2√3a² but should have read σ_s = -e/2√3a². These errors have now been corrected in the online version of the Letter.