Proximity of Iron Pnictide Superconductors to a Quantum Tricritical Point

TL;DR

This paper investigates the magnetic quantum critical point in doped LaFeAsO, revealing it is near a quantum tricritical point where phase transition order changes, with implications for understanding iron pnictide superconductors.

Contribution

The study provides ab initio coefficients for a Landau analysis, demonstrating the proximity of LaFeAsO to a quantum tricritical point and discussing experimental implications.

Findings

LaFeAsO is close to a quantum tricritical point.

The phase transition nature changes from first to second order.

Comparison with effective field theory offers experimental insights.

Abstract

We determine the nature of the magnetic quantum critical point in the doped LaFeAsO using a set of constrained density functional calculations that provide ab initio coefficients for a Landau order parameter analysis. The system turns out to be remarkably close to a quantum tricritical point, where the nature of the phase transition changes from first to second order. We compare with the effective field theory and discuss the experimental consequences.