Line nodes in the energy gap of high-temperature superconducting BaFe_2(As_{1-x}P_x)_2 from penetration depth and thermal conductivity measurements

TL;DR

This study provides evidence of line nodes in the energy gap of BaFe$_2$(As$_{1-x}$P$_x$)$_2$ superconductors through penetration depth and thermal conductivity measurements, highlighting different pairing states with similar critical temperatures.

Contribution

It demonstrates the presence of line nodes in the energy gap of BaFe$_2$(As$_{1-x}$P$_x$)$_2$, contrasting with nodeless gaps in similar compounds, revealing diverse pairing states in Fe-based high-$T_c$ superconductors.

Findings

Line nodes confirmed in BaFe$_2$(As$_{1-x}$P$_x$)$_2$

Nodeless gap in (Ba,K)Fe$_2$As$_2$

Different pairing states with similar $T_c$

Abstract

We report magnetic penetration depth and thermal conductivity data for high-quality single crystals of BaFe$_2$(As$_{1-x}$P$_{x}$)$_2$ ($T_c=30$\,K) which provide strong evidence that this material has line nodes in its energy gap. This is distinctly different from the nodeless gap found for (Ba,K)Fe$_2$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 $T_c$.