Hidden Ladder in SrMoO$_3$/SrTiO$_3$ Superlattices: Experiments and Theoretical Calculations

TL;DR

This study investigates the electronic structure of artificially constructed SrMoO$_3$/SrTiO$_3$ superlattices, revealing a hidden ladder band structure similar to Sr$_3$Mo$_2$O$_7$, but no superconductivity was observed.

Contribution

The paper demonstrates the creation of SrMoO$_3$/SrTiO$_3$ superlattices with a hidden ladder band structure through experiments and first-principles calculations, providing insights into their electronic properties.

Findings

Band structure resembles Sr$_3$Mo$_2$O$_7$

Suppressed dispersion with more SrTiO$_3$ layers

No superconductivity observed down to 0.1 K

Abstract

A double-layered perovskite oxide Sr$_3$Mo$_2$O$_7$ is considered a "hidden ladder" system with wide and narrow bands near the Fermi level, for which high-$T_{\rm c}$ 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 SrMoO$_3$ block through artificial superlattices with the insulating SrTiO$_3$ block, (SrMoO$_3$)$_m$/(SrTiO$_3$)$_t$ ($m = 2, 4$; $t = 4$). First-principles calculations for bilayered SrMoO$_3$ ($m = 2$) exhibit a wide-narrow band structure near the Fermi level, which bears a close resemblance to Sr$_3$Mo$_2$O$_7$. The dispersion along the $k_z$ direction is strongly suppressed by increasing the number of the SrTiO$_3$ 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.