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

doi:10.1103/PhysRevB.96.201108

paper

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

arXiv:1707.06599 · doi:10.1103/PhysRevB.96.201108

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 $T^{*} ≃ 155$ 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 $T_{FL} ≃ 75$ 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 $d_{x y}$ orbital. Our results advocate for Kondo-type screening as the mechanism for the orbital-selective incoherent-coherent crossover in hole-overdoped KFe $_{2}$ As $_{2}$ .

Manuscript: 5 pages with 3 figures. Supplementary material: 6 pages with 5 figures and 1 table

Observation of an Emergent Coherent State in the Iron-Based Superconductor KFe2​As2​

Abstract

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