An external magnetic field can actually enhance superconductivity, pro vided it is strong enough. If only few lowest Landau levels are occupied, the quasi 1D nature of the electronic motion leads to an enhancement of transition temperature. The orbital frustration of the order parameter is much simplified in this limit. This limit of superconductivity, of great interest in itself, can also be used as a starting point to study orbital frustration in familiar, “low-field”, strongly type II superconductors. I briefly review some of the characteristics of superconductivity in high magnetic fields.
AbstractThe correlation in type-II superconductors between the creep rate S and the Second Magnetization Peak (SMP) phenomenon which produces an increase in Jc, as a function of the field (H), has been investigated at different temperatures by starting from the minimum in S(H) and the onset of the SMP phenomenon detected on a FeSe0.5Te0.5 sample. Then the analysis has been extended by considering the entire S(H) curves and comparing our results with those of many other superconducting materials reported in literature. In this way, we find evidence that the flux dynamic mechanisms behind the appearance of the SMP phenomenon in Jc(H) are activated at fields well below those where the critical current starts effectively to increase. Moreover, the found universal relation between the minimum in the S(H) and the SMP phenomenon in Jc(H) shows that both can be attributed to a sequential crossover between a less effective pinning (losing its effectiveness at low fields) to a more effective pinning (still acting at high fields), regardless of the type-II superconductor taken into consideration.
A precursor mechanism triggering the second magnetization peak phenomenon in superconducting materials