# Three superconducting phases with different categories of pairing in hole- and electron-doped LaFeAs$_{1-x}$P$_x$O

## TL;DR

This study identifies three distinct superconducting phases in LaFeAs$_{1-x}$P$_x$O, each with different Fermi surface topologies and pairing mechanisms, highlighting the complex interplay of electronic correlations in iron-based superconductors.

## Contribution

It reveals the existence of three superconducting phases with different Fermi surface topologies and pairing mechanisms in LaFeAs$_{1-x}$P$_x$O, advancing understanding of their electronic correlations.

## Key findings

- Three superconducting phases with distinct Fermi surface topologies.
- T-linear resistivity correlates with maximum $T_c$ across phases.
- Variety in phase diagrams indicates multiple orbital contributions.

## Abstract

The phase diagram of LaFeAs$_{1-x}$P$_x$O system has been extensively studied through hole- and electron-doping as well as As/P-substitution. It has been revealed that there are three different superconducting phases with different Fermi surface (FS) topologies and thus with possibly different pairing glues. One of them is well understood as spin fluctuation-mediated superconductivity within a FS nesting scenario. Another one with the FSs in a bad nesting condition must be explained in a different context such as orbital or spin fluctuation in strongly correlated electronic system. In both phases, $T$-linear resistivity was commonly observed when the superconducting transition temperature $T_{\rm c}$ becomes the highest value, indicating that the strength of bosonic fluctuation determines $T_{\rm c}$. In the last superconducting phase, the nesting condition of FSs and the related bosonic fluctuation are moderate. Variety of phase diagram characterizes the multiple orbital nature of the iron-based superconductors which are just near the boundary between weak and strong correlation regimes.