Interface superconductivity in complex metal-oxide heterostructures

Interface superconductivity in oxide superstructures (SS) proposes new paths to explore further the mechanism for high-T_c superconductors allowing the manipulation of their electronic properties, but also discovering novel artificial materials [1], e.g., electron transfer from LaFeO₃ (LFO) to electron-doped Sm₂CuO₄ was explored in SS grown by RF sputtering [2]. In the present study, we have grown SS of infinite-layer SrCuO₂ (SCO) and LFO as well as SS of electron-doped (Sr,Nd)CuO₂ (SNCO) and LFO by pulsed-laser deposition with various thicknesses and annealing conditions. The coherent growth of SCO/LFO and SNCO/LFO SS has been confirmed by X-ray diffraction. Resistivity and Hall effect measurements confirm superconductivity in selected samples of SNCO/LFO SS, but no superconductivity and little doping by charge transfer has been observed in SCO/LFO SS. However, we observe a strong correlation between the critical temperature and the thickness of the SS subcomponents for SNCO/LFO SS. Our findings indicate that charge transfer may not be playing a significant role behind the superconductivity in these structures.
[1] A. Ohtomo et al., Nature 427, 423-426 (2004)
[2] F.Y. Bruno et al., Adv. Mat. 25, 1468 (2013)