We present a study of the Berezinskii-Kosterlitz-Thouless (BKT) transition in mildly disordered NbN nanoporous (NP) films. The measured superfluid stiffness, $J_s$, is found to be much lower than that predicted considering a reduced geometric area. For a 5 nm thick NP film, a distinct BKT transition is observed. By fitting the experimental data via the BKT renormalization-group equations, we show how both $J_s$ and the vortex-core energy, $\mu$, decrease in the presence of nanopores. The variation of $J_s$ and $\mu$ is also reproduced theoretically via Monte Carlo numerical simulations on a 2D diluted XY model. Our results show that nanopore geometries effectively enhance the 2D nature of the superconducting films, increasing the parameter space to explore the BKT physics while offering a pathway to systematically control the two energy scales, $J_s$ and $\mu$, that govern the vortex physics in these systems.

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• Superconductivity
• Superfluid density
• XY model
• Cryogenics
• Monte Carlo methods
• Resistivity measurements
• Sputtering
• Susceptibility measurements