Intrinsic pinning and the critical current scaling of clean epitaxial Fe(Se,Te) thin films

Abstract

We report on the transport properties of clean, epitaxial Fe(Se,Te) thin films prepared on Febuffered MgO (001) single crystalline substrates by pulsed laser deposition. Near Tc a steep slope of the upper critical field for H||ab was observed (74.1 T/K), leading to a very short out-of-plane coherence length, ξc(0), of 0.2 nm, yielding 2ξc(0) ≈ 0.4 nm. This value is shorter than the interlayer distance (0.605 nm) between Fe-Se(Te) planes, indicative of modulation of the superconducting order parameter along the c-axis. An inverse correlation between the power law exponent N of the electric field-current density(E-J) curve and the critical current density, Jc, has been observed at 4 K, when the orientation of H was close to the ab-plane. These results prove the presence of intrinsic pinning in Fe(Se,Te). A successful scaling of the angular dependent Jc and the corresponding exponent N can be realized by the anisotropic Ginzburg Landau approach with appropriate Γ values 2∼3.5. The temperature dependence of Γ behaves almost identically to that of the penetration depth anisotropy.

Influence of substrate type on transport properties of superconducting FeSe0.5Te0.5thin films

“…Similar c-axis peaks in J c (θ) have been observed for films deposited on CaF 2 substrate [14]. However, no additional peaks have been observed in FeSe 0.5 Te 0.5 films on LAO [11] and Fe-buffered MgO substrates [15][16]. In this work, FeSe 0.5 Te 0.5 thin films were deposited on CaF 2 , LAO and MgO single crystalline substrates in order to further elucidate the role of the substrate for the superconducting properties.…”

“…Fe-buffered MgO with a much shorter coherence length ξ c [16], follows the trend and magnitude of the penetration depth anisotropy γ λ instead. It is difficult and not reasonable to scale J c of the film on bare MgO, due to the extra c-axis peak in J c related to the line defects as confirmed by TEM images.…”

Angular flux creep contributions in YBa2Cu3O7−δ nanocomposites from electrical transport measurements

“…Therefore, we observe the appearance of the S(θ)-peak at this temperature, which spans an orientation width of 5° and widens as temperature decreases. However, at low temperatures (50 K in this case), a narrow S(θ)-dip arises at the center of the S(θ)-peak, indicative of a lock-in transition 27 , also reported in other electrical transport studies 23,25 . This latter effect shows that at low temperatures, the thermal energy k B T is not high enough to cause movement of vortices through DK formation when they lie almost parallel to the CuO 2 planes.…”

Impact of thickness on microscopic and macroscopic properties of Fe-Te-Se superconductor thin films

“…26,27 However, our EDX results (seen TABLE.I) show the radio of Te/Se deviates from the reported optimal value FeTe 0.5 Se 0.5 with the increase of the deposition temperature. It means that deposition temperature may affect in other ways to modulate superconductor properties, which still need more study.…”