Enhancement of critical current density and mechanism of vortex pinning in H⁺-irradiated FeSe single crystal

Abstract

In this report, we comprehensively study the effect of H + irradiation on the critical current density, J c , and vortex pinning in FeSe single crystal. It is found that the value of J c for FeSe is enhanced more than twice after 3-MeV H + irradiation. The scaling analyses of the vortex pinning force based on the Dew-Hughes model reveal that the H + irradiation successfully introduce point pinning centers into the crystal. We also find that the vortex creep rates are strongly suppressed after irradiation. Detailed analyses of the critical current dependent pinning energy based on the collective creep theory and extend Maley's method show that the H + irradiation enhances the value of J c before the flux creep, and also reduces the size of flux bundle, which will further reduce the field dependence of J c due to vortex motion.

Second magnetization peak effect, vortex dynamics and flux pinning in 112-type superconductor Ca0.8La0.2Fe1−xCoxAs2

“…Thus, the E–P crossover is not a sufficient condition for SMP. Absence of SMP is reported in FeSe crystal with innate superconductivity even though similar E–P crossover is observed3749. SMP only appears when deformation of vortex lines wins the competition and this competition is related to many factors which we will discuss in the following paragraphs.…”

“…Due to the similar layered structures, E–P crossover has been commonly demonstrated in different types of IBSs. In cases of Ca 1− x Na x Fe 2 As 2 , FeSe, and H + -irradiated FeSe374249, clear signal of E–P crossover has been witnessed, while no SMP occurs. This absence of SMP should be attributed to other factors including the numbers of weak pinning centers and also relatively large ξ c /d ratio.…”

“…Furthermore, even though the self-field J s is relatively high in Co-co-doping 112 crystal, weak collective pinning is predominant in the present system. Applications of additive techniques such as irradiation and hydrostatic pressure should still be helpful for further J s enhancement4951.…”

Universal lower limit on vortex creep in superconductors

“…high [5][6][7][8]19 , which raised an important question: precisely what should we expect and how much lower can we go?…”

“…8,23 , where the data for FeSe was extracted from S(H) at different temperatures 9 and we measured Rb0.8Fe1.6SeS 41 . All previous studies of creep in Fe-SCs have been performed on single crystals [5][6][7][8]14,19,22,23,32,[42][43][44] , where self-fields (Hsf ∝ Jc × thickness) are higher than in our films. Consequently, we perform a direct comparison at !…”