Unconventional superconductivity and antiferromagnetic quantum critical behavior in the isovalent-doped BaFe2(As1-xPx)2

TL;DR

This study investigates the evolution of spin dynamics in BaFe$_2$(As$_{1-x}$P$_x$)$_2$ using NMR, revealing a quantum-critical point where antiferromagnetic fluctuations are enhanced and likely crucial for high-temperature superconductivity.

Contribution

It provides direct evidence of a quantum-critical point in BaFe$_2$(As$_{1-x}$P$_x$)$_2$, linking antiferromagnetic fluctuations to high-$T_c$ superconductivity.

Findings

Antiferromagnetic fluctuations are enhanced near the AF phase.

The magnetic ordering temperature $ heta$ vanishes at optimal doping.

Evidence supports the role of AF quantum criticality in superconductivity.

Abstract

Spin dynamics evolution of BaFe$_2$(As$_{1-x}$P$_x$)$_2$ was probed as a function of P concentration via $^{31}$P NMR. Our NMR study reveals that two-dimensional antiferromagnetic (AF) fluctuations are notably enhanced with little change in static susceptibility on approaching the AF phase from the superconducting dome. Moreover, magnetically ordered temperature $\theta$ deduced from the relaxation rate vanishes at optimal doping. These results provide clear-cut evidence for a quantum-critical point (QCP), suggesting that the AF fluctuations associated with the QCP play a central role in the high-$T_c$ superconductivity.