Study of flux pinning mechanism under hydrostatic pressure in optimally doped (Ba,K)Fe(2)As(2) single crystals

Strong pinning depends on the pinning force strength and number density of effective defects. Using the hydrostatic pressure method, we demonstrate here that hydrostatic pressure of 1.2 GPa can significantly enhance flux pinning or the critical current density (J(c)) of optimally doped Ba(0.6)K(0.4)Fe(2)As(2) crystals by a factor of up to 5 in both low and high fields, which is generally rare with other J(c) enhancement techniques. At 4.1 K, high pressure can significantly enhance J(c) from 5 × 10(5 )A/cm(2) to nearly 10(6 )A/cm(2) at 2 T, and from 2 × 10(5 )A/cm(2) to nearly 5.5 × 10(5 )A/cm(2) at 12 T. Our systematic analysis of the flux pinning mechanism indicates that both the pinning centre number density and the pinning force are greatly increased by the pressure and enhance the pinning. This study also shows that superconducting performance in terms of flux pinning or J(c) for optimally doped superconducting materials can be further improved by using pressure.