Suppression of antiferromagnetic spin fluctuations in the collapsed tetragonal phase of CaFe2As2

TL;DR

This study demonstrates that antiferromagnetic spin fluctuations are suppressed in the collapsed tetragonal phase of CaFe2As2 under pressure, indicating a strong link between spin dynamics and superconductivity in iron arsenides.

Contribution

It provides experimental evidence that the collapsed tetragonal phase lacks antiferromagnetic fluctuations, highlighting their role in superconductivity mechanisms.

Findings

Spin fluctuations are suppressed in the cT phase.

Resistivity decreases upon transition to cT phase.

Absence of static magnetic order in cT phase.

Abstract

Inelastic neutron scattering measurements of CaFe2As2 under applied hydrostatic pressure show that the antiferromagnetic spin fluctuations observed in the ambient pressure, paramagnetic, tetragonal (T) phase are strongly suppressed, if not absent, in the collapsed tetragonal (cT) phase. These results are consistent with a quenched Fe moment in the cT phase and the strong decrease in resistivity observed upon crossing the boundary from the T to cT phase. The suppression or absence of static antiferromagnetic order and dynamic spin fluctuations in the non-superconducting cT phase supports the notion of a coupling between spin fluctuations and superconductivity in the iron arsenides.