Characterizing quasiparticle recombination time in epitaxial NbN thin films on (1 0 0) MgO

Abstract

We report on the vortex dynamics of a 14 nm thick (1 0 0) NbN thin film grown by reactive sputtering on (1 0 0) MgO. The film exhibits a smooth surface and a critical temperature (Tc) of 16.2 K. Thickness was confirmed by low-angle X-ray reflectivity, and two-dimensional behavior in the upper critical field was observed with the magnetic field parallel to the surface. The quasiparticle recombination time (τ) near Tc was determined using I-V curves, showing a thermally activated process, with τ decreasing as temperature rises, reaching ~20 ps at 14 K.These results are compared with literature values and analyzed considering intrinsic factors (superconducting properties, substrate thermal conductivity) and extrinsic factors (vortex pinning, disorder). Our findings offer insights into vortex dynamics and the Larkin-Ovchinnikov instability in epitaxial NbN thin films, highlighting their relevance for cryogenic devices.