Critical Role Played by Interface Engineering in Weakening Thickness Dependence of Superconducting and Structural Properties of FeSe_0.5Te_0.5-Coated Conductors

Abstract

Increasing the thickness of a superconducting layer and simultaneously reducing the thickness effect in iron-based superconducting coated conductors are particularly essential for improving the critical current I c . Here, for the first time, we have deposited high-performance FeSe 0.5 Te 0.5 (FST) superconducting films up to 2 μm on LaMnO 3 -buffered metal tapes by pulsed laser deposition. An interface engineering strategy, alternating growth of a 10 nm-thick nonsuperconducting FST seed layer and a 400 nmthick FST superconducting layer, was employed to guarantee the crystalline quality of the films with thicknesses of the order of micrometers, resulting in a highly biaxial texture with grain boundary misorientation angle less than the critical value θ c ∼ 9°. Moreover, the thickness effect, that the critical current density (J c ) shows a clear dependence on thickness as in cuprates, is reduced by the interface engineering. Also, the maximum J c was found for a 400 nm-thick film with 1.3 MA/cm 2 in self-field at 4.2 K and 0.71 MA/cm 2 (H∥ab) and 0.50 MA/cm 2 (H∥c) at 9 T. Anisotropic Ginzburg−Landau scaling indicates that the major pinning centers vary from correlated to uncorrelated as the film thickness increases, while the thickness effect is most likely related to the weakening of flux pinning by the fluctuation of charge-carrier mean free path (δl) and strengthening of flux pinning caused by the variation of superconducting transition temperature (δT c ) due to offstoichiometry with thickness.

Enhanced Superconductivity and Critical Current Density Due to the Interaction of InSe2 Bonded Layer in (InSe2)0.12NbSe2

“…Notably, the J c value reaches a remarkable value of 8.2 × 10 5 A/cm 2 at 2 K, which is four times larger than that observed in pure NbSe 2 . The J c value of the (InSe 2 ) 0.12 NbSe 2 sample is larger than those of other TMD superconductors, such as NbS 2 , Cu x TiSe 2 , and Fe x NbSe 2 , − and is comparable to other unconventional superconductors such as cuprate and iron-based superconductors. − …”

Properties and Applications of Iron–Chalcogenide Superconductors

“…The FeSe0.5Te0.5 on a rolling-assisted biaxially textured substrate (RABiTS) exhibited Tc > 20 K. The self-field Jc reached 1 MA/cm 2 at 4.2 K, and Jc remained around 1 × 10 5 A/cm 2 under a high magnetic field of 30 T. Sylva et al found that the CeO2 layer plays an important role in preventing the element diffusion from the Ni-W substrate and inducing in-plane texture [81,82]. Song et al adopted an interface engineering strategy to mitigate the thickness effect, successfully fabricating micron-thick FeSe0.5Te0.5 superconducting films on IBAD-LaMnO3-buffered metal tapes [65]. Unlike the continuous growth mode, the alternating growth of a 10 nm thick seed layer and a 400 nm thick FST superconducting layer ensures the crystalline quality of FeSe0.5Te0.5 films (see Figure 17a-c).…”