Berezinskii-Kosterlitz-Thouless transition in rhenium nitride films

The quest to manipulate and understand superconductivity demands exploring diverse materials and unconventional behaviors. Here, we investigate the Berezinskii-Kosterlitz-Thouless (BKT) transition in ReNx thin films, demonstrating their emergence as a compelling platform for studying this pivotal phenomenon. By systematically varying synthesis parameters, we achieve ReNx films exhibiting a BKT transition comparable to what is known from NbNx meander structure films. Detailed current-voltage measurements unlock the intrinsic parameters of the BKT transition, revealing the critical role of suppressed superconducting volume in pushing ReNx towards the two-dimensional limit. Utilizing this two-dimensional electron system, we employ Beasley-MooijOrlando theory to extract the vortex unbinding transition temperature and superelectron density at the critical point. Further confirmation of the BKT transition is obtained through temperature-dependent resistivity, current- voltage, and magnetoresistance measurements. Our findings suggest that native disorder and inhomogeneity within ReNx thin films act to suppress long-range coherence, ultimately driving the system towards the BKT regime. This work establishes ReNx as a promising material for exploring BKT physics and paves the way for tailoring its properties for potential applications in superconducting devices.