Expansion of the tetragonal magnetic phase with pressure in the iron-arsenide superconductor Ba{1-x}KxFe2As2

TL;DR

This study investigates how applying pressure influences the tetragonal magnetic phase in Ba{1-x}KxFe2As2, revealing that pressure significantly expands this phase and suggesting its fluctuations could be linked to superconductivity pairing.

Contribution

It provides the first detailed analysis of pressure effects on the tetragonal magnetic phase in Ba{1-x}KxFe2As2, highlighting its potential role in superconductivity.

Findings

Pressure expands the tetragonal magnetic phase.

The stripe-like magnetic phase shrinks under pressure.

Tetragonal phase fluctuations may be involved in pairing mechanism.

Abstract

In the temperature-concentration phase diagram of most iron-based superconductors, antiferromagnetic order is gradually suppressed to zero at a critical point, and a dome of superconductivity forms around that point. The nature of the magnetic phase and its fluctuations is of fundamental importance for elucidating the pairing mechanism. In Ba{1-x}KxFe2As2 and Ba{1-x}NaxFe2As2, it has recently become clear that the usual stripe-like magnetic phase, of orthorhombic symmetry, gives way to a second magnetic phase, of tetragonal symmetry, near the critical point, between x = 0.24 and x = 0.28. Here we report measurements of the electrical resistivity of Ba{1-x}KxFe2As2 under applied hydrostatic pressures up to 2.75 GPa, for x = 0.22, 0.24 and 0.28. We track the onset of the tetragonal magnetic phase using the sharp anomaly it produces in the resistivity. In the temperature-concentration phase diagram of Ba{1-x}KxFe2As2, we find that pressure greatly expands the tetragonal magnetic phase, while the stripe-like phase shrinks. This raises the interesting possibility that the fluctuations of the former phase might be involved in the pairing mechanism responsible for the superconductivity.