Evolution of pinning mechanism and vortex pattern driven by thickness effect in superconducting films

Abstract The thickness-dependent suppression of current-carrying capacity in superconducting thin films necessitates a fundamental understanding of the underlying mechanisms to optimize their practical applications. Here, we systematically investigate the evolution of pinning mechanisms and vortex patterns in Pb films as a function of thickness. Through combined macroscopic transport measurements and microscopic magnetic force microscopy (MFM) imaging, we reveal a transition from δ l -dominated to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>δ</mml:mi> <mml:msub> <mml:mi>T</mml:mi> <mml:mtext>c</mml:mtext> </mml:msub> </mml:mrow> </mml:math> -dominated pinning mechanisms with increasing film thickness. MFM observations demonstrate enhanced vortex lattice ordering in thicker films, indicating weakened pinning strength. Statistical analysis of vortex configurations under varying magnetic fields further confirms that reduced pinning dominance allows vortex–vortex repulsion to govern lattice alignment, approaching the ideal triangular Abrikosov lattice. The pinning energy and pinning force both show a decreasing trend with increasing film thickness. Critical current density ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>J</mml:mi> <mml:mtext>c</mml:mtext> </mml:msub> </mml:mrow> </mml:math> ) measurements corroborate these findings, showing a decline in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>J</mml:mi> <mml:mtext>c</mml:mtext> </mml:msub> </mml:mrow> </mml:math> with thickness as δ l pinning diminishes. This study establishes a direct correlation between thickness-induced shifts in pinning mechanisms, vortex dynamics, and macroscopic superconducting properties. Our results provide critical insights into the thickness effect in superconducting films, advancing strategies for optimizing high-performance superconducting devices.