Optical and transport properties of NbN thin films revisited

Abstract

Highly disordered NbN thin films exhibit promising superconducting and optical properties. Despite extensive study, discrepancies in its basic electronic properties persist. Analysis of the optical conductivity of disordered ultra-thin NbN films, obtained from spectroscopic ellipsometry by standard Drude-Lorentz model, provides inconsistent parameters. We argue that this discrepancy arise from neglecting the presence of quantum corrections to conductivity in the IR range. To resolve this matter, we propose a modification to the Drude-Lorentz model, incorporating quantum corrections. The parameters obtained from the modified model are consistent not only with transport and superconducting measurements but also with ab initio calculations. The revisited values describing conduction electrons, which differ significantly from commonly adopted ones, are the electron relaxation rate $\Gamma \approx 1.8\text{eV}/\hslash$, the Fermi velocity $v_F\approx 0.7\times 10^6{\text{ms}}^{-1}$ and the electron density of states $N(E_F)=2$states of both spins/eV/$V_{\text{f.u.}}$.

arXiv comment10 pages, 6 figures

References in corpus (20)

• Granular Electronic Systems
• Microscopic origin of the Drude-Smith model
• Superconducting properties and Hall Effect of epitaxial NbN thin films
• Phase diagram of a strongly disordered s-wave superconductor, NbN, close to the metal-insulator transition
• Emergence of nanoscale inhomogeneity in the superconducting state of a homogeneously disordered conventional superconductor, NbN
• Superconducting properties of very high quality NbN thin films grown by high temperature chemical vapor deposition
• Microscopic interpretation of the Dynes formula for the tunneling density of states
• Electrodynamics of the Superconducting State in Ultra-Thin Films at THz Frequencies
• Characterization of thin-film NbN superconductor for single-photon detection by transport measurements
• Electron-phonon coupling, superconductivity and nontrivial band topology in NbN polytypes
• Spectroscopic evidence for strong correlations between local superconducting gap and local Altshuler-Aronov density-of-states suppression in ultrathin NbN films
• Electron energy relaxation in disordered superconducting NbN films
• Anomalous gap edge dissipation in disordered superconductors on the brink of localization
• Displaced Drude peak and bad metal from the interaction with slow fluctuations
• Thermodynamic properties of the Dynes superconductors
• Niobium nitride-based normal metal-insulator-superconductor tunnel junction microthermometer
• Momentum-resolved electronic band structure and offsets in an epitaxial NbN/GaN superconductor/semiconductor heterojunction
• Far-infrared electrodynamics of thin superconducting NbN film in magnetic field
• Observation of quantum corrections to conductivity up to optical frequencies
• A numerical extrapolation method for complex conductivity of disordered metals

Cited by in corpus (2)

• Nernst effect and its thickness dependence in superconducting NbN films
• Photothermal resistivity alignment of optical fibers to SNSPD