Tuning the electronic properties of ultrathin La_0.7Sr_0.3MnO₃ films by interfacing with superconducting EuBa₂Cu₃O_7-δ

Interfaces between transition-metal oxides provide an intriguing platform for modifying the ground states of single constituent materials and creating desired functionalities for applications in oxide-based electronics. Here, we demonstrate that the metallic and ferromagnetic responses of La_0.7Sr_0.3MnO₃ (LSMO) films with thicknesses less than 4 nm, which are insulating when grown directly on SrTiO₃ substrates, can be restored through interfacing with a high-temperature cuprate superconductor EuBa₂Cu₃O_7-δ (EBCO). We carried out scanning tunneling microscopy and spectroscopy measurements on the electronic structure of LSMO/EBCO bilayers with thickness of LSMO layer varying from 2 to 7 nm. Our results suggest that the transfer of holes from EBCO to LSMO, caused by the difference in their work functions, is responsible for driving LSMO film with thickness of only five unit cells to the metallic state.