Observation of an Emergent Coherent State in the Iron-Based Superconductor KFe${}_2$As${}_2$

Run Yang, Zhiping Yin, Yilin Wang +5

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…