Hidden Ladder in SrMoO₃/SrTiO₃ Superlattices: Experiments and Theoretical Calculations

Abstract

A double-layered perovskite oxide Sr3Mo2O7 is considered a "hidden ladder" system with wide and narrow bands near the Fermi level, for which high-Tc superconductivity is expected. However, the difficulty in synthesis, especially in the preparation of samples without oxygen deficiency, can hinder the observation of superconductivity. In this study, we constructed a double-layer SrMoO3 block through artificial superlattices with the insulating SrTiO3 block, (SrMoO3)m/(SrTiO3)t (m = 2, 4; t = 4). First-principles calculations for bilayered SrMoO3 (m = 2) exhibit a wide-narrow band structure near the Fermi level, which bears a close resemblance to Sr3Mo2O7. The dispersion along the kz direction is strongly suppressed by increasing the number of the SrTiO3 layers, t. However, no superconductivity is observed down to 0.1 K. We discuss the absence of the superconductivity for the present films on the basis of results of scanning transmission electron microscopy and band structure calculations.