论文标题
$ _ {2} $
Anisotropic optical properties of detwinned BaFe$_{2}$As$_{2}$
论文作者
论文摘要
在$ t _ {\ rm n} \ rm n} \ simeq 138 $ k上的宽频率范围内检查了$ _2 $的大型，deatwin的单晶的光学特性。各向同性；晶格模式在$ t _ {\ rm n} $上方显示弱极化依赖性。对于$ t <t _ {\ rm n} $，由于自由载体响应而引起的光电率是各向异性的，沿着$ a $ axis的$ b $ axis沿$ \ simeq 30 $ MEV的$ B $ axis;在此能量上方，光导率由带间贡献支配，这些贡献似乎是各向同性的。清楚地观察到了低于$ t _ {\ rm n} $以下低能红外活动模式的分裂，并且可以使用新模式的极化调制来估计晶体为$ \ simeq 70 $％％detwinned。高频模式的强度在$ t _ {\ rm n} $下方的下分支的强度增加了三倍，并且几乎是沉默的上部分支。
The optical properties of a large, detwinned single crystal of BaFe$_2$As$_2$ have been examined over a wide frequency range above and below the structural and magnetic transition at $T_{\rm N}\simeq 138$ K. Above $T_{\rm N}$ the real part of the optical conductivity and the two infrared-active lattice modes are almost completely isotropic; the lattice modes show a weak polarization dependence just above $T_{\rm N}$. For $T<T_{\rm N}$, the optical conductivity due to the free-carrier response is anisotropic, being larger along the $a$ axis than the $b$ axis below $\simeq 30$ meV; above this energy the optical conductivity is dominated by the interband contributions, which appear to be isotropic. The splitting of the low-energy infrared-active mode below $T_{\rm N}$ is clearly observed, and the polarization modulation of the new modes may be used to estimate that the crystal is $\simeq 70$% detwinned. The high-frequency mode, with a threefold increase in strength of the lower branch below $T_{\rm N}$ and nearly silent upper branch, remains enigmatic.
