Fabrication of oxide/FeSe multilayer films using pulsed laser deposition

In this study, we demonstrate the successful fabrication of ${\mathrm{TiO}}_{2}/\mathrm{FeSe}/{\mathrm{SrTiO}}_{3}$ and ${\mathrm{TiO}}_{2}/\mathrm{FeSe}/{\mathrm{LaAlO}}_{3}$ heterostructures using PLD. When the growth rates were sufficiently low, anatase ${\mathrm{TiO}}_{2}$, which has been reported to induce superconductivity in FeSe, could be grown epitaxially on FeSe. For ${\mathrm{TiO}}_{2}/\mathrm{FeSe}/{\mathrm{SrTiO}}_{3}$ with FeSe layers thicker than 5 nm, the $\mathrm{FeSe}/{\mathrm{TiO}}_{2}$ interface was clean, as confirmed by the observation of Laue fringes around the FeSe(001) reflection. Although a thinner FeSe layer is expected to enhance ${T}_{\mathrm{c}}$, we could not observe such behavior because it was difficult to realize interfacial superconductivity while growing anatase ${\mathrm{TiO}}_{2}$. Most strikingly, superconductivity appeared when ${\mathrm{TiO}}_{2}$ was deposited on $\mathrm{FeSe}/{\mathrm{LaAlO}}_{3}$, clearly demonstrating that the interaction between the top oxide layer and underlying FeSe can induce superconductivity. This work demonstrates the feasibility of fabricating FeSe/oxide superlattices by PLD, establishing a platform for the exploration of interfacial superconductivity in iron-based superconductors.