Strong Competition of Superconducting and Magnetic Order Parameters in Ba1-xNaxFe2As2

TL;DR

This study investigates the coexistence and competition of magnetic and superconducting orders in Ba1-xNaxFe2As2, revealing microscopic coexistence and doping-dependent suppression of magnetic moments, with implications for understanding iron-based superconductors.

Contribution

It provides the first detailed muon spin relaxation analysis of magnetic and superconducting interplay in Ba1-xNaxFe2As2 across different doping levels.

Findings

Microscopic coexistence of magnetic order and superconductivity in underdoped samples.

Suppression of magnetic moments below Tc in nearly optimally doped samples.

Superfluid density consistent with two nodeless s-wave gaps in optimally doped samples.

Abstract

We study the interplay of magnetic and superconducting order in single crystalline hole doped Ba1-xNaxFe2As2 using muon spin relaxation. We find microscopic coexistence of magnetic order and superconductivity. In a strongly underdoped specimen the two forms of order coexist without any measurable reduction of the ordered magnetic moment by superconductivity, while in a nearly optimally doped sample the ordered magnetic moment is strongly suppressed below the superconducting transition temperature. This coupling can be well described within the framework of an effective two-band model incorporating inter- and intra-band interactions. In optimally doped Ba1-xNaxFe2As2 we observe no traces of static or dynamic magnetism and the temperature dependence of the superfluid density is consistent with two s-wave gaps without nodes.