Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy ofSciences, Beijing 100190, People’s Republic of China.
J Phys Condens Matter. 2012 Jul 25;24(29):294202. doi: 10.1088/0953-8984/24/29/294202.
We report optical spectroscopic measurements on electron- and hole-doped BaFe2As2. We show that the compounds in the normal state are not simple metals. The optical conductivity spectra contain, in addition to the free carrier response at low frequency, a temperature-dependent gap-like suppression at fairly high energy scale near 0.6 eV. This suppression evolves with the As–Fe–As bond angle induced by electron or hole doping. Furthermore, the feature becomes much weaker in the Fe-chalcogenide compounds. We elaborate that the feature is mainly caused by the strong Hund's rule coupling effect between the itinerant electrons and localized electron moment arising from the multiple Fe 3d orbitals. The coupling strength changes with the environment of the Fe atom. Our experiments demonstrate the coexistence of itinerant and localized electrons in iron-based compounds, which would then lead to a more comprehensive picture of the metallic magnetism in the materials.
我们报告了电子和空穴掺杂 BaFe2As2 的光学光谱测量结果。我们表明，正常状态下的化合物不是简单的金属。光学电导率谱除了在低频下的自由载流子响应外，还在相当高的能量尺度（接近 0.6eV）上存在温度相关的带隙样抑制。这种抑制随着电子或空穴掺杂引起的 As–Fe–As 键角而演变。此外，在 Fe-硫属化合物中，该特征变得弱得多。我们详细说明该特征主要是由巡游电子和局域电子矩之间的强烈 Hund 规则耦合效应引起的，这是由多个 Fe 3d 轨道引起的。耦合强度随 Fe 原子的环境而变化。我们的实验证明了铁基化合物中巡游电子和局域电子的共存，这将为材料中的金属磁性提供更全面的认识。
