Temperature dependence of resistivity and Hall coefficient in strongly disordered NbN thin films

Abstract

We report the temperature dependence of resistivity (ρ) and Hall coefficient (R_H) in the normal state of homogeneously disordered epitaxial NbN thin films with k_Fl∼1.68–10.12. The superconducting transition temperature (T_c) of these films varies from 2.7 to 16.8 K. While our least disordered film displays usual metallic behavior, for all the films with k_Fl≤8.13, both dρ/dT and dR_H/dT are negative up to 285 K. We observe that R_H(T) varies linearly with ρ(T) for all the films and [R_H(T)−R_H(285 K)/R_H(285 K)]=γ[ρ(T)−ρ(285 K)/ρ(285 K)], where γ=0.68±0.11. Measurements performed on a 2-nm-thick Be film show similar behavior with γ=0.69. This behavior is inconsistent with existing theories of localization and e−e interactions in a disordered metal.