A possible superconductor-like state at elevated temperatures near metal electrodes in an LaAlO₃/SrTiO₃ interface

We experimentally investigated the transport properties near metal electrodes installed on a conducting channel in a LaAlO₃/SrTiO₃ interface. The local region around the Ti and Al electrodes has a higher electrical conductance than that of other regions, where the upper limits of the temperature and magnetic field can be well defined. Beyond these limits, the conductance abruptly decreases, as in the case of a superconductor. The samples with the Ti- or Al-electrode have an upper-limit temperature of approximately 4 K, which is 10 times higher than the conventional superconducting critical temperature of LaAlO₃/SrTiO₃ interfaces and delta-doped SrTiO₃. This phenomenon is explained by the mechanism of electron transfer between the metal electrodes and electronic d-orbitals in the LaAlO₃/SrTiO₃ interface. The transferred electrons trigger a phase transition to a superconductor-like state. Our results contribute to the deep understanding of the superconductivity in the LaAlO₃/SrTiO₃ interface and will be helpful for the development of high-temperature interface superconductors.