Comment on "Quantum Criticality and Nodal Superconductivity in the FeAs-Based Superconductor KFe$_2$As$_2$"

TL;DR

This paper critiques a previous claim of a quantum critical point in KFe$_2$As$_2$, arguing that the observed resistivity behavior and recent experimental results do not support the existence of such a QCP.

Contribution

It challenges prior interpretations of resistivity data and recent dHvA measurements as evidence for a field-induced quantum critical point in KFe$_2$As$_2$.

Findings

Resistivity T^{1.5} dependence alone is insufficient as evidence for a QCP.

Broad resistive transitions complicate the interpretation of quantum criticality.

Recent dHvA results do not support the existence of a QCP in the studied material.

Abstract

In a recent Letter [J. K. Dong et al., Phys. Rev. Lett. 104, 087005 (2010)], Dong \textit{et al}. have observed a $T^{1.5}$ dependence of resistivity $\rho$ in KFe$_2$As$_2$ at the upper critical field $B_{c2}$ = 5 T parallel to the c axis and have suggested the existence of a field-induced quantum critical point (QCP) at $B_{c2}$. In this comment, we argue that observation of a $T^{1.5}$ dependence of $\rho$ in a sample showing broad resistive transitions does not constitute evidence for a QCP and that recent dHvA results do not support the proposed QCP.