Line nodes in the energy gap of superconductingBaFe2(As1−xPx)2single crystals as seen via penetration depth and thermal conductivity

We report magnetic penetration depth and thermal-conductivity data for high-quality single crystals of ${\text{BaFe}}_2{\left({\text{As}}_{1-x}{\text{P}}_x\right)}_2\left(T_c=30\text{K}\right)$ which provide strong evidence that this material has line nodes in its energy gap. This is distinctly different from the nodeless gap found for $\left(\text{Ba},\text{K}\right){\text{Fe}}_2{\text{As}}_2$ which has similar $T_c$ and phase diagram. Our results indicate that repulsive electronic interactions play an essential role for Fe-based high-$T_c$ superconductivity but that uniquely there are distinctly different pairing states, with and without nodes, which have comparable $T_c$.