Phase diagram as a function of doping level and pressure in Eu$_{1-x}$La$_x$Fe$_2$As$_2$ system

TL;DR

This study maps the phase diagram of Eu$_{1-x}$La$_x$Fe$_2$As$_2$ as a function of doping and pressure, revealing how pressure suppresses SDW and influences magnetic and superconducting phases.

Contribution

It provides the first detailed phase diagram of Eu$_{1-x}$La$_x$Fe$_2$As$_2$ under varying doping and pressure, highlighting the interplay between magnetic order and superconductivity.

Findings

Pressure suppresses SDW and structural transitions.

Superconductivity coexists with SDW at low pressure.

Eu$^{2+}$ AFM order coexists with superconductivity.

Abstract

We establish the phase diagram of Eu$_{1-x}$La$_x$Fe$_2$As$_2$ system as a function of doping level x and the pressure by measuring the resistivity and magnetic susceptibility. The pressure can suppress the spin density wave (SDW) and structural transition very efficiently, while enhance the antiferromagnetic (AFM) transition temperature T$_N$ of Eu$^{2+}$. The superconductivity coexists with SDW order at the low pressure, while always coexists with the Eu$^{2+}$ AFM order. The results suggests that Eu$^{2+}$ spin dynamics is disentangeld with superconducting (SC) pairing taken place in the two-dimensional \emph{Fe-As} plane, but it can strongly affect superconducting coherence along c-axis.