Field-tuned superconductor-insulator transitions and Hall resistance in thin polycrystalline MoN films.

We report on the superconductor-insulator transitions (SITs) of disordered molybdenum nitride (MoN) thin films on (1 0 0) MgO substrates as a function of the film thickness and magnetic fields. The T-c of the superconducting MoN films, which exhibit a sharp superconducting transition, monotonically decreases as the normal state R-sq increases with a decreasing film thickness. For several films with different thicknesses, we estimate the critical field H-c and the product z upsilon similar or equal to 0.6 of the dynamical exponent z and the correlation length exponent. using a finite scaling analysis. The value of this product can be explained by the (2 + 1) XY model. We found that the Hall resistance Delta R-xy(H) is maximized when the magnetic field satisfies H-HP(T) proportional to vertical bar 1 - T/T-C0 vertical bar in the superconducting state and also in the normal states owning to the superconducting fluctuation corresponding to the ghost critical magnetic field. We measured the Hall conductivity delta sigma(xy)(H) = sigma(xy)(H) - sigma(n)(xy) and fit the Gaussian approximation theory for dsxy(H) to the experimental data. Agreement between the data and the theory beyond Hc suggests the survival of the Cooper pair in the insulating region of the SIT.