Anomalous Enhancement of the Superconducting Transition Temperature in   Electron-Doped Cuprate Heterostructures
  The superconducting transition temperature $T_{c}$ of multilayers of electron-doped cuprates, composed of underdoped (or undoped) and overdoped La% $_{2-x}$Ce$_{x}$CuO$_{4}$ (LCCO) and Pr$_{2-x}$Ce$_{x}$CuO$_{4}$ (PCCO) thin films, is found to increase significantly with respect to the $T_{c}$ of the corresponding single-phase films. By investigating the critical current density of superlattices with different doping levels and layer thicknesses, we find that the $T_{c}$ enhancement is caused by a redistribution of charge over an anomalously large distance. 
K. Jin, P. Bach, X. H. Zhang, U. Grupel, E. Zohar, I. Diamant, Y.   Dagan, S. Smadici, P. Abbamonte, and R. L. Greene
cond-mat.supr-con cond-mat.mtrl-sci