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arXiv 1306.4257cond-mat.mtrl-sci
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自旋-轨道相互作用对单层、双层和体MoS2中激子效应的影响

Effect of spin-orbit interaction on the excitonic effects in single-layer, double-layer, and bulk MoS2

Alejandro Molina-Sánchez, Davide Sangalli, Kerstin Hummer, Andrea Marini, Ludger Wirtz

摘要:

我们提出了收敛的从头计算的光学吸收光谱的单层,双层,和散装的MoS $_2$。准粒子能量计算(在GW近似的水平上)和吸收光谱的计算(在Bethe-Salpeter方程的水平上)都明确地包括自旋轨道耦合,使用完整的自旋Kohn-Sham波函数作为输入。在没有激子效应的情况下,吸收光谱将具有阶跃函数的形式,对应于二维抛物带色散的联合态密度。这种配置文件是由一个明显的约束激子峰以下的连续开始变形。在单层的情况下,峰被自旋-轨道相互作用分裂,在双层和体MoS $_2$的情况下,(主要)被层间相互作用分裂。因此,在这三种情况下产生的吸收光谱非常相似,但光谱的解释不同。在光谱中的差异可以看到约3 eV的单,双电层的光谱是由一个强束缚激子为主。

英文摘要:

We present converged ab-initio calculations of the optical absorption spectra of single-layer, bi-layer, and bulk MoS$_2$. Both the quasiparticle-energy calculations (on the level of the GW approximation) and the calculation of the absorption spectra (on the level of the Bethe-Salpeter equation) explicitly include spin-orbit coupling, using the full spinorial Kohn-Sham wave-functions as input. Without excitonic effects, the absorption spectra would have the form of a step-function, corresponding to the joint-density of states of a parabolic band-dispersion in 2D. This profile is deformed by a pronounced bound excitonic peak below the continuum onset. The peak is split by spin-orbit interaction in the case of single-layer and (mostly) by inter-layer interaction in the case of double-layer and bulk MoS$_2$. The resulting absorption spectra are thus very similar in the three cases but the interpretation of the spectra is different. Differences in the spectra can be seen around 3 eV where the spectra of single and double-layer are dominated by a strongly bound exciton.

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