Cyclotron resonance and mass enhancement by electron correlation in KFe$_2$As$_2$

TL;DR

This study uses cyclotron resonance measurements on KFe$_2$As$_2$ to reveal significant electron correlation effects that enhance effective mass, highlighting the importance of both intra- and interband interactions.

Contribution

First direct observation of mass enhancement due to electron correlation in KFe$_2$As$_2$ via cyclotron resonance, comparing it with dHvA results.

Findings

CR effective mass (3.4m_e) is larger than dHvA mass

Mass enhancement is due to electronic correlations

Both intra- and interband correlations contribute

Abstract

Cyclotron resonance (CR) measurements for the Fe-based superconductor KFe$_2$As$_2$ are performed. One signal for CR is observed, and is attributed to the two-dimensional $\alpha$ Fermi surface at the $\Gamma$ point. We found a large discrepancy in the effective masses of CR [(3.4$\pm$0.05)$m_e$ ($m_e$ is the free electron mass)] and de-Haas van Alphen (dHvA) results, a direct evidence of mass enhancement due to electronic correlation. A comparison of the CR and dHvA results shows that both intra- and interband electronic correlations contribute to the mass enhancement in KFe$_2$As$_2$.