Na$_3$Bi基三维Dirac电子体系中的光吸收窗口
Optical absorption window in Na$_3$Bi based three-dimensional Dirac electronic system
AI总结：
本文利用Boltzmann能量平衡方程和$\mathbf{k}\cdotp \mathbf{p}$模型研究Na$_3$Bi基三维Dirac电子体系，发现可调光吸收窗口及栅压开关带间吸收的机制。
摘要：
我们对基于Na$_3$Bi的三维Dirac电子体系（3DDES）的光电性质进行了详细理论研究。光学电导采用由Boltzmann方程导出的能量平衡方程进行计算，其中电子Hamilton量取自简化的$\mathbf{k}\cdotp \mathbf{p}$方法。我们发现，对于短波长辐照，Na$_3$Bi中的光吸收主要来自带间电子跃迁。与graphene中观察到的普适光学电导不同，基于Na$_3$Bi的3DDES的光学电导依赖于辐射频率，而不依赖于温度、载流子密度和电子弛豫时间。在约5 $μm<λ<$ 200 $μm$的辐射波长范围内，发现了一个光吸收窗口。这与在graphene中观察到的情况相似。该吸收窗口的位置和宽度取决于光的偏振方向，并敏感地依赖于温度、载流子密度和电子弛豫时间。特别地，我们证明了通过施加栅极电压可以开启和关闭带间光吸收通道。这意味着，与graphene类似，基于Na$_3$Bi的3DDES也可应用于红外电光调制器。我们的理论发现有助于深入理解最近发现的3DDES的基本光电性质。
英文摘要：
We present a detailed theoretical study of the optoelectronic properties of a Na$_3$Bi-based three-dimensional Dirac electronic system (3DDES). The optical conductivity is evaluated using the energy-balance equation derived from a Boltzmann equation, where the electron Hamiltonian is taken from a simplified $\mathbf{k}\cdotp \mathbf{p}$ approach. We find that for short-wavelength irradiation, the optical absorption in Na$_3$Bi is mainly due to inter-band electronic transitions. In contrast to the universal optical conductance observed for graphene, the optical conductivity for Na$_3$Bi based 3DDES depends on the radiation frequency but not on temperature, carrier density and electronic relaxation time. In the radiation wavelength regime of about 5 $μm<λ<$ 200 $μm$, an optical absorption window is found. This is similar to what is observed in graphene. The position and width of the absorption window depend on the direction of the light polarization and sensitively on temperature, carrier density, and electronic relaxation time. Particularly, we demonstrate that the inter-band optical absorption channel can be switched on and off by applying the gate voltage. This implies that similar to graphene, Na$_3$Bi based 3DDES can also be applied in infrared electro-optical modulators. Our theoretical findings are helpful in gaining an in-depth understanding of the basic optoelectronic properties of recently discovered 3DDESs.
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