A route for a strong increase of critical current in nanostrained iron-based superconductors

Abstract

The critical temperature Tc and the critical current density Jc determine the limits to large-scale superconductor applications. Superconductivity emerges at Tc. The practical current-carrying capability, measured by Jc, is the ability of defects in superconductors to pin the magnetic vortices, and that may reduce Tc. Simultaneous increase of Tc and Jc in superconductors is desirable but very difficult to realize. Here we demonstrate a route to raise both Tc and Jc together in iron-based superconductors. By using low-energy proton irradiation, we create cascade defects in FeSe0.5Te0.5 films. Tc is enhanced due to the nanoscale compressive strain and proximity effect, whereas Jc is doubled under zero field at 4.2 K through strong vortex pinning by the cascade defects and surrounding nanoscale strain. At 12 K and above 15 T, one order of magnitude of Jc enhancement is achieved in both parallel and perpendicular magnetic fields to the film surface.

Fe-based superconducting thin films on metallic substrates: Growth, characteristics, and relevant properties

“…Additionally, the phase formation has to be optimized so that the full potential of the films on single crystals can be achieved on tape. On the other hand, J c -H of Fe(Se,Te) on RABiTS 89 is almost comparable to that of the pinning-enhanced Fe(Se,Te) thin film 48 ( fig. 17(c)).…”

Effects of heavy-ion irradiation on FeSe

“…Although the value of J c for the pure FeSe single crystal is relatively small, the Te-doped FeSe tapes with J c over 10 6 A/cm 2 under self-field and over 10 5 A/cm 2 under 30 T at 4.2 K have already been fabricated, which is promising for applications [57]. Recently, 1.5 times enhancement of J c was achieved in FeTe 0.5 Se 0.5 thin film by irradiating with protons [58]. Our current results indicate that heavy-ion irradiation with a small dose may be effective in the further enhancement of J c for the tapes and thin films of FeSe system.…”

Critical current density and vortex pinning mechanism of Lix(NH3)yFe2Te${}_{1.2}$Se${}_{0.8}$ single crystals

“…If the quality of parent compounds Fe(Te, Se) can be improved further, the J c of LiFeTeSe-122 could be even higher. On the other hand, the Fe(Te, Se) films can have larger J c than single crystals because of various kinds of external factors, such as interface effects, nonmagnetic/magnetic point/nanorod defects/inclusions introduced during preparation process of films, pinning of grain boundaries etc [39,40,41,42]. Moreover, the enhancement of T c has been observed in Fe(Te, Se) films and it is inextricably linked to the strain induced during the epitaxial growth [40,43].…”