Effects of Neutron Irradiation on Magnesium Diboride Thin Films

The effect of disorder on normal state and superconducting properties is studied in a series of neutron irradiated magnesium diboride thin films. Irradiation increases residual resistivity by more than two orders of magnitude and progressively decreases critical temperature down to the complete suppression of superconductivity. In this disorder-controlled set of samples, we analyze magnetoresistivity, extracting the scattering times in each band, and upper critical field. H_c2 is extremely high and only weakly depends on resistivity at low irradiation level. We propose a simple explanation for this puzzling topic, and we discuss the importance of reaching high magnetic field to correctly extrapolate H_c2(0).