Electronic properties of 3 d transitional metal pnictides: A comparative study by optical spectroscopy

作者：Buwen Cheng, Bin Hu, R. Y. Chen, Gang Xu, P. Zheng, Jinming Luo, N. L. Wang · 发表于：Physical Review B · 年份：2012 · DOI：10.1103/physrevb.86.134503 · 被引用次数：48 · 研究领域：Iron-based superconductors research、Rare-earth and actinide compounds、Intellectual Capital and Performance Analysis

Single-crystalline KFe${}_{2}$As${}_{2}$ and Ca$T$${}_{2}$As${}_{2}$ ($T=\text{Fe}$, Co, Ni, and Cu) are synthesized and investigated by resistivity, susceptibility, and optical spectroscopy. It is found that CaCu${}_{2}$As${}_{2}$ exhibits a similar transition to the lattice abrupt collapse transitions discovered in CaFe${}_{2}$(As${}_{1\ensuremath{-}x}$P${}_{x}$)${}_{2}$ and Ca${}_{1\ensuremath{-}x}$$R$${}_{x}$Fe${}_{2}$As${}_{2}$ ($R$ $=$ rare-earth element). The resistivity of KFe${}_{2}$As${}_{2}$ and Ca$T$${}_{2}$As${}_{2}$ ($T=\text{Fe}$, Co, Ni, and Cu) approximately follows the similar T${}^{2}$ dependence at low temperature, but the magnetic behaviors vary with different samples. Optical measurement reveals that the optical response of CaCu${}_{2}$As${}_{2}$ is not sensitive to the transition at 50 K, with no indication of development of a new energy gap below the transition temperature. Using Drude-Lorentz model, we find that two Drude terms, a coherent one and an incoherent one, can fit the low-energy optical conductivity of KFe${}_{2}$As${}_{2}$ and Ca$T$${}_{2}$As${}_{2}$ ($T=\text{Fe}$, Co, and Ni) very well. However, in CaCu${}_{2}$As${}_{2}$, which is a $sp$-band metal, the low-energy optical conductivity can be well described by a coherent Drude term. Lack of the incoherent Drude term in CaCu${}_{2}$As${}_{2}$ may be attributed to a weaker electronic correlation than in KFe${}_{2}$As${}_{2}$ and Ca$T$${}_{2}$As${}_{2}$ ($T=\text{Fe}$, Co, and Ni). Spectral w...