Maximizing the critical current of YBCO superconductors
*Petriina Paturi1

We present a way to reach the maximum possible critical current density, Jc, for YBa2Cu3O6+x (YBCO) thin films. This value is found to be around ten times the currently reached values. It is found that the Jc(0 T) is governed by the mean free path of the electrons, as is the critical temperature, Tc. The Jc in field, on the other hand, is governed by flux pinning and can be enhanced by optimizing the size and distribution of the non-superconducting nanoinclusions. Optimizing both the mean free path and the pinning structure, the maximum values can be reached.

In practise, this means that the superconductor in between the pinning sites should be as
crystallographically clean as possible to increase the electron mean free path. The optimal pinning site size and density depend on the planned magnetic field. Fot a field of 5 T, the pinning site diameter should be around 10 nm and the distance 20 nm, i.e. the density should be quite high.

Keywords: YBCO thin films, critical current density, flux pinning, electron mean free path