Unique phase diagram with narrow superconducting dome in EuFe${}_2$(As${}_{1-x}$P${}_x$)${}_2$ due to Eu${}^{2+}$ local magnetic moments

The interplay between superconductivity and Eu${}^{2+}$ magnetic moments in EuFe${}_2$(As${}_{1-x}$P${}_x$)${}_2$ is studied by electrical resistivity measurements under hydrostatic pressure on $x=0.13$ and $x=0.18$ single crystals. We can map hydrostatic pressure to chemical pressure $x$ and show, that superconductivity is confined to a very narrow range $0.18\le x\le 0.23$ in the phase diagram, beyond which ferromagnetic (FM) Eu ordering suppresses superconductivity. The change from antiferro- to FM Eu ordering at the latter concentration coincides with a Lifshitz transition and the complete depression of iron magnetic order.