Electron Energy Relaxation Times in Superconducting Tungsten Rhenium-based Thin Films

We report on the evaluation of the electron energy relaxation times both in pure WRe and nitrogen-doped WReN superconducting films. The former are crystalline and exhibit a superconducting critical temperature, Tc ∼ 4.5 K, while the latter have larger Tc ∼ 5.6 K and an amorphous nature. Magnetoconductivity measurements were performed on films of different thicknesses to extract different electron relaxation times, and the results were analyzed by taking into account superconducting fluctuation and weak localization effects. The electron–electron (τe−e), electron– phonon (τe−ph), electron–fluctuation (τe−fl) scattering times, as well as the τe−ph/τe−e ratio are intermediate between those estimated for other W-based and nitride superconducting films typically employed as superconducting single photon detectors (SSPDs). Furthermore, we also observed a larger value of τe−ph/τe−e ratio for WReN compared to the WRe film of the same thickness, suggesting its better potential as SSPDs. These results establish WRe films as a possible contender for future SSPDs working in the low energy photon regime.