High-field critical current enhancement by irradiation induced correlated and random defects in (Ba0.6K0.4)Fe2As2

Abstract

Mixed pinning landscapes in superconductors are emerging as an effective strategy to achieve high critical currents in high, applied magnetic fields. Here, we use heavy-ion and proton irradiation to create correlated and point defects to explore the vortex pinning behavior of each and combined constituent defects in the iron-based superconductor Ba0.6K0.4Fe2As2 and find that the pinning mechanisms are non-additive. The major effect of p-irradiation in mixed pinning landscapes is the generation of field-independent critical currents in very high fields. At 7 T ‖ c and 5 K, the critical current density exceeds 5 MA/cm2.

Effects of heavy-ion irradiation on FeSe

“…The temperature dependence of the penetration depth in Co or K substituted BaFe 2 As 2 was found to change after heavy-ion irradiation, consistent with the s ± scenario [29,30]. On the other hand, the columnar defects created by heavy-ion irradiation are also strong pinning centers due to the geometrical similarity with vortices, which are already proved to be effective to the enhancement of critical current density J c [26,27,[31][32][33]. Their controllability is also advantageous in the study of vortex physics.…”

“…In the case of correlated disorders created by heavy-ion irradiation, such as columnar defects, an obvious suppression of T c together with the increase in the normal state resistivity has been reported in cuprates [25]. However, the T c shows only a small or nondetectable change in iron pnictides [26][27][28][29][30][31][32][33]. The temperature dependence of the penetration depth in Co or K substituted BaFe 2 As 2 was found to change after heavy-ion irradiation, consistent with the s ± scenario [29,30].…”

Giant increase of critical current density and vortex pinning in Mn doped KxFe2−ySe2 single crystals

“…It is noted both ZFCP and SMP effects have been observed in MHLs of S-doped K x Fe 2Ày Se 2 single crystal (only for H k c), 23 "11" iron-chalcogenide and "122" iron-arsenic SCs. [4][5][6][7]25,26 Moreover, after annealing and quenching the crystals at around 673 K, 14,15,18,24 the superconducting properties of pristine sample can be enormously improved, as comparable to the Mn doped samples. Here, the symmetric features of MHLs in S1-quenched samples are similar to those reported, 14,15,24 suggesting that the dominant pinning sources are from bulk instead of surface barriers after thermal treatment.…”

“…3 Among iron-based superconducting families, 2 the so called "122" iron-based SCs with ThCr 2 Si 2 structure are particularly attractive and promising for future high field applications due to their high T c (up to 38 K), upper critical field (l 0 H c2 $ 100 T), low anisotropy (C $ 2), and capacity of carrying large critical current density (J c $ 10 6 A/cm 2 ). [4][5][6][7] Sharing a similar crystal structure with "122" SCs, the mono-ion intercalated A x Fe 2-y Se 2 (A ¼ K, Rb, Cs, Tl) SCs with T c $ 30 K have received considerable attention because of their intriguing properties. 8 Very high l 0 H c2 values (>50 T at T ¼ 0 K) have been revealed by the high field magnetotransports and radiofrequency (rf) contactless penetration depth measurements on K x Fe 2Ày Se 2 and (Tl,Rb) x Fe 2Ày Se 2 single crystals.…”

“…17 It was reported that the J c values could be improved by quenching or Te/S doping, 14,15,20-24 but still one or two orders smaller than "11" iron-chalcogenide and "122" iron-arsenic SCs. [4][5][6][7]25,26 To improve the J c and evaluate the high field performance of A x Fe 2Ày Se 2 SCs, the study of vortex pinning mechanism needs to be carried out especially on high quality samples. So far, there are only few investigations on the vortex pinning in "122"-like K x Fe 2 Se 2 SCs.…”