Pressure-induced magnetism in iron-based superconductors $A$Fe$_2$As$_2$ ($A=$ K, Cs, Rb)

TL;DR

This study reveals that in iron-based superconductors $A$Fe$_2$As$_2$, magnetism emerges under pressure near the critical point and coexists with superconductivity, indicating a transition between different pairing symmetries.

Contribution

It provides experimental evidence of pressure-induced magnetism and coexistence with superconductivity, supporting a transition between different pairing states in $A$Fe$_2$As$_2$.

Findings

Magnetism appears just below the critical pressure $P_c$.

Magnetism and superconductivity coexist at pressures above $P_c$.

Results support a transition between different pairing symmetries.

Abstract

The magnetic properties of iron-based superconductors $A$Fe$_2$As$_2$ ($A=$K, Cs, and Rb), which are characterized by the V-shaped dependence of the critical temperature ($T_{\rm c}$) on pressure ($P$) were studied by means of the muon spin rotation/relaxation technique. In all three systems studied the magnetism was found to appear for pressures slightly below the critical one ($P_{\rm c}$), i.e. at pressure where $T_{\rm c}(P)$ changes the slope. Rather than competing, magnetism and superconductivity in $A$Fe$_2$As$_2$ are coexisting at $P\gtrsim P_{\rm c}$ pressure region. Our results support the scenario of a transition from one pairing state to another, with different symmetries on either side of $P_{\rm c}$.