1. School of Physical Science and Technology, China University of Mining and Technology, Xuzhou 221116, China 2. Low Carbon Energy Institute, China University of Mining and Technology, Xuzhou 221116, China 3. Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, China 4. Department of Physics, Yunnan University, Kunming 650091, China
The electronic structures of a MoS2 monolayer are investigated with the all-electron first principle calculations based on the density functional theory (DFT) and the spin-orbital couplings (SOCs). Our results show that the monolayer MoS2 is a direct band gap semiconductor with a band gap of 1.8 eV. The SOCs and d-electrons in Mo play a very significant role in deciding its electronic and optical properties. Moreover, electronic elementary excitations are studied theoretically within the diagrammatic self-consistent field theory. Under random phase approximation, it shows that two branches of plasmon modes can be achieved via the conduction-band transitions due to the SOCs, which are different from the plasmons in a two-dimensional electron gas and graphene owing to the quasi-linear energy dispersion in single-layer MoS2. Moreover, the strong optical absorption up to 105 cm−1 and two optical absorption edges I and II can be observed. This study is relevant to the applications of monolayer MoS2 as an advanced photoelectronic device.
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