Growth of High-Quality Superconducting FeSe_0.5Te_0.5 Films on Pb(Mg_1/3Nb_2/3)_0.7Ti_0.3O₃ and Electric-Field Modulation of Superconductivity

Heterostructures composed of superconductor and ferroelectrics (SC/FE) are very important for manipulating the superconducting property and applications. However, growth of high-quality superconducting iron chalcogenide films is challenging because of their volatility and FE substrate with rough surface and large lattice mismatch. Here, we report a two-step growth approach to get high-quality FeSe_0.5Te_0.5 (FST) films on FE Pb(Mg_1/3Nb_2/3)_0.7Ti_0.3O₃ with large lattice mismatch, which show superconductivity at only around 10 nm. Through a systematic study of structural and electric transport properties of samples with different thicknesses, a mechanism to grow high-quality FST is discovered. Moreover, electric-field-induced remarkable change of T_c (superconducting transition temperature) is demonstrated in a 20 nm FST film. This work paves the way to grow high-quality films which contain volatile element and have large lattice mismatch with the substrate. It is also helpful for manipulating the superconducting property in SC/FE heterostructures.