arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2103.08676cond-mat.mes-hallcond-mat.mtrl-sci
收藏

垂直叠层MoSe $_2$ /WSe $_2$异质双层膜的层间激子谱

Interlayer excitonic spectra of vertically stacked MoSe$_2$/WSe$_2$ heterobilayers

Roland Gillen

摘要:

垂直堆叠的MoSe $_2$ /WSe $_2$异质结构的光谱包含额外的“层间”激子峰,其在单个单层材料中不存在,并且在面外方向上表现出显著的空间电荷分离。在前人研究的基础上,我们采用多体微扰理论方法模拟和分析了MoSe $_2$ /WSe $_2$异质双层膜的激子光谱,考虑了动量直接激子和动量间接激子。我们发现,层间激子的小振子强度和相应的光学响应与层间效应有显著的依赖关系,并使“亮”层间激子的辐射寿命在5- 200 ns(T= 4K)之间.通过求解有限动量Bethe-Salpeter方程,我们预测最低能量的激发应该是间接带隙(K $\rightarrow$ Q)上的间接激子,结合能为220.meV.然而,与最近的磁光实验和以前的理论研究一致,我们的有效激子Landé g因子的模拟表明,低能动量间接激子没有实验观察到的MoSe $_2$ /WSe $_2$异质结构。我们进一步揭示了“层间”C激子的存在与显着的激子结合能和光学振子强度,这是类似于突出的带嵌套激子在单层和少层过渡金属二硫属化物。

英文摘要:

The optical spectra of vertically stacked MoSe$_2$/WSe$_2$ heterostructures contain additional 'interlayer' excitonic peaks that are absent in the individual monolayer materials and exhibit a significant spatial charge separation in out-of-plane direction. Extending on a previous study, we used a many-body perturbation theory approach to simulate and analyse the excitonic spectra of MoSe$_2$/WSe$_2$ heterobilayers with three stacking orders, considering both momentum-direct and momentum-indirect excitons. We find that the small oscillator strengths and corresponding optical responses of the interlayer excitons are significantly stacking-dependent and give rise to high radiative lifetimes in the range of 5-200\,ns (at T=4\,K) for the 'bright' interlayer excitons. Solving the finite-momentum Bethe-Salpeter Equation, we predict that the lowest-energy excitation should be an indirect exciton over the fundamental indirect band gap (K$\rightarrow$Q), with a binding energy of 220\,meV. However, in agreement with recent magneto-optics experiments and previous theoretical studies, our simulations of the effective excitonic Landé g-factors suggest that the low-energy momentum-indirect excitons are not experimentally observed for MoSe$_2$/WSe$_2$ heterostructures. We further reveal the existence of 'interlayer' C excitons with significant exciton binding energies and optical oscillator strengths, which are analogous to the prominent band nesting excitons in mono- and few-layer transition-metal dichalcogenides.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑