The low-temperature variation in the London penetration depth for a number of iron-pnictide and iron-chalcogenide superconductors is nearly quadratic, $\Delta \lambda \left(T\right)=\beta T^n$ with $n\approx 2$. The coefficient in this dependence shows a robust scaling, $\beta \propto 1/T_c^3$ across different families of these materials. We associate the scaling with a strong pair breaking. The same mechanism has recently been suggested to explain the scalings of the specific-heat jump, $\Delta C\propto T_c^3$ [Bud’ko et al., Phys. Rev. B 79, 220516(R) (2009)], and the slopes of the upper critical field, $d{H}_{c2}/dT\propto T_c$ in these materials [Kogan, Phys. Rev. B 80, 214532 (2009)]. This suggests that thermodynamic and electromagnetic properties of the iron-based superconductors can be described within a strong pair-breaking scenario (this work).

• Received 25 February 2010

DOI:https://doi.org/10.1103/PhysRevB.81.180501