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arXiv · 1707.06599

Observation of an Emergent Coherent State in the Iron-Based Superconductor KFe$_\mathbf{2}$As$_\mathbf{2}$

Run Yang·Zhiping Yin·Yilin Wang·Yaomin Dai·Hu Miao·Bing Xu·Xianggang Qiu·Christopher C. Homes
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Abstract

The optical properties of KFe$_2$As$_2$ have been measured for light polarized in the a-b planes over a wide temperature and frequency range. Below $T^\ast\simeq 155$ K, where this material undergoes an incoherent-coherent crossover, we observe a new coherent response emerging in the optical conductivity. A spectral weight analysis suggests that this new feature arises out of high-energy bound states. Below about $T_{\rm FL} \simeq 75$ K the scattering rate for this new feature is quadratic in temperature, indicating a Fermi-liquid response. Theory calculations suggest this crossover is dominated by the $d_{xy}$ orbital. Our results advocate for Kondo-type screening as the mechanism for the orbital-selective incoherent-coherent crossover in hole-overdoped KFe$_2$As$_2$.

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Run Yang, Zhiping Yin, Yilin Wang, Yaomin Dai, Hu Miao, Bing Xu, Xianggang Qiu, Christopher C. Homes. 2017-07-20. Observation of an Emergent Coherent State in the Iron-Based Superconductor KFe$_\mathbf{2}$As$_\mathbf{2}$. https://doi.org/10.1103/physrevb.96.201108

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