Many-body theory of optical absorption in doped two-dimensional semiconductors
Many-body theory of optical absorption in doped two-dimensional semiconductors
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DOI：
10.1103/physrevb.99.125421
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发表时间：
2019-03-14
影响因子：
3.7
通讯作者：
Reichman, David R.
中科院分区：
文献类型：
--
作者：
Chang, Yao-Wen;Reichman, David R.
本文用多体方法研究了电子掺杂二维半导体的吸收光谱。光吸收模型的多体散射哈密顿描述了一个激子浸没在费米海。电子与激子之间的相互作用近似为一个有效的散射势，并通过求解激子绿色函数计算光谱。从这个方法，trion可以被指定为一个电子激子散射过程的束缚态，和掺杂依赖的光谱中观察到的现象可以归因于与费米海的相互作用引起的几个多体效应。虽然多体散射哈密顿量不能精确求解，我们减少了两个限制可解的情况下的问题。第一种方法通过电子和激子之间的简单散射过程近似完整的多体问题，通过求解Bethe-Salpeter方程（BSE）获得自能。另一种方法假设激子的质量无限大，使得多体散射哈密顿量简化为Mahan-Nozieres-De Dominant（MND）模型。激子绿色的功能，然后可以精确地数值求解的行列式配方，与光谱，显示在高掺杂浓度的费米边缘奇异性的签名。激子和trion线形状的全掺杂依赖性和温度依赖性通过这两种近似的方法进行模拟，与彼此和实验预期的结果进行比较。
In this paper, we use a many-body approach to study the absorption spectra of electron-doped two-dimensional semiconductors. Optical absorption is modeled by a many-body scattering Hamiltonian which describes an exciton immersed in a Fermi sea. The interaction between electron and exciton is approximated by an effective scattering potential, and optical spectra are calculated by solving for the exciton Green's function. From this approach, the trion can be assigned as a bound state of an electron-exciton scattering process, and the doping-dependent phenomena observed in the spectra can be attributed to several many-body effects induced by the interaction with the Fermi sea. While the many-body scattering Hamiltonian cannot be solved exactly, we reduce the problem to two limiting solvable situations. The first approach approximates the full many-body problem by a simple scattering process between the electron and the exciton, with a self-energy obtained by solving a Bethe-Salpeter equation (BSE). An alternate approach assumes an infinite mass for the exciton, such that the many-body scattering Hamiltonian reduces to a Mahan-Nozieres-De Dominicis (MND) model. The exciton Green's function can then be solved numerically exactly by a determinantal formulation, with an optical spectra that show signatures of the Fermi-edge singularity at high doping densities. The full doping dependence and temperature dependence of the exciton and trion line shapes are simulated via these two approximate approaches, with the results compared to each other and to experimental expectations.