Roles of electron mean free path and flux pinning in optimizing the critical current in YBCO superconductors
P. Paturi, H. Huhtinen
Abstract
Abstract We present a way to reach the maximum possible critical current density, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>J</mml:mi> <mml:mrow> <mml:mi mathvariant="normal">c</mml:mi> </mml:mrow> </mml:msub> </mml:math> , for YBa 2 Cu 3 O <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi/> <mml:mrow> <mml:mn>6</mml:mn> <mml:mo>+</mml:mo> <mml:mi>x</mml:mi> </mml:mrow> </mml:msub> </mml:math> (YBCO) thin films. This value is found to be around ten times the currently reached values. It is found that the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>J</mml:mi> <mml:mrow> <mml:mi mathvariant="normal">c</mml:mi> </mml:mrow> </mml:msub> </mml:math> (0 T) is governed by the mean free path of the electrons, as is the critical temperature, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>T</mml:mi> <mml:mrow> <mml:mi mathvariant="normal">c</mml:mi> </mml:mrow> </mml:msub> </mml:math> . The <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>J</mml:mi> <mml:mrow> <mml:mi mathvariant="normal">c</mml:mi> </mml:mrow> </mml:msub> </mml:math> in field, on the other hand, is governed by flux pinning sites and can be enhanced by optimizing the size and distribution of the non-superconducting nanoinclusions. By optimizing both the mean free path and the pinning structure, the maximum values can be reached.