High-Tc superconducting thin films with composition control on a sub-unit cell level; the effect of the polar nature of the cuprates

Inspired by the work of Ohtomo and Hwang in 2004, we shed new light on thin films of layered cuprate high-Tc superconductors (HTS). In principle all HTS materials consist of charged perovskite-like layers which in thin films can lead to polar discontinuities at the interfaces of different materials. The resulting charge redistribution has to occur but we expect it to be far more complex than in the LaAlO3/SrTiO3 system since copper can be multivalent. This makes it hard to predict what will happen in terms of transport or even magnetic properties compared to the 'simple' insulator LaAlO3. Nevertheless, we point out that the picture of systems of charged layers is important and necessary to fully understand heterostructures of these complex materials.