Effects of 1-MeV proton irradiation in Hg-based cuprate thin films

We have studied the effects of 1-Mev proton irradiation on both superconducting properties and normal state resistivity of high-quality HgBa₂CaCu₂O_6+δ (Hg-1212) and HgBa₂Ca₂Cu₃O_8+δ (Hg-1223) thin films. At low proton doses, we observed a linear decrease of the superconducting transition temperature Tc and a linear increase of the extrapolated residual resistivity as proton dose is increased. This is consistent with observations of other high-Tc superconductors while a lower dose threshold for suppressing the superconductivity is found in Hg-1212 and Hg-1223 films. To explain the linear dose dependence of Tc, we propose a model based on the proximity effect. An enhancement of up to 90% in the critical current density at low fields has also been observed in these films at low proton fluences that do not significantly degrade Tc.