The effect of impurities on the Superheating field of Type II superconductors

We calculate the superheating field $H_s(T)$, the maximum field at which the Meissner state exists, for a type-II, single band s-wave superconductor with nonmagnetic and magnetic impurities. $H_s(T)$ was calculated for the entire temperature region $0c_g$, the quasiparticle gap $E_g(c)$ appears at $H=H_s$ so that $E_g \sim 0.410\Delta$ in the dirty limit. This feature can be important for the nonlinear surface resistance at strong rf fields $H\sim H_s$.