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Abstract:
Pressure is well known to significantly raise the superconducting
transition temperature, T-c in both iron pnictides and cuprate based
superconductors. Little work has been done, however, on how pressure can
affect the flux pinning and critical current density in the Fe-based
superconductors. Here, we propose to use hydrostatic pressure to
significantly enhance flux pinning and T-c in polycrystalline pnictide
bulks. We have chosen Sr4V2O6Fe2As2 polycrystalline samples as a case
study. We demonstrate that the hydrostatic pressure up to 1.2 GPa can
not only significantly increase T-c from 15 K (underdoped) to 22 K, but
also significantly enhance the irreversibility field, H-irr, by a factor
of 4 at 7 K, as well as the critical current density, J(c), by up to 30
times at both low and high fields. It was found that pressure can induce
more point defects, which are mainly responsible for the J(c)
enhancement. Our findings provide an effective method to significantly
enhance T-c, J(c), Hirr, and the upper critical field, H-c2, for other
families of Fe-based superconductors in the forms of wires/tapes, films,
and single crystal and polycrystalline bulks.
