等离激元增强的石墨烯光吸收

石墨烯中等离激元具有特殊的光电性质,其和入射光的强烈耦合可以引起光吸收的增强.本文基于时域有限差分法和多体自洽场理论研究了等离激元对处于光学谐振腔中的石墨烯光吸收的影响.由于石墨烯中等离激元与入射光动量和能量不匹配而不能直接相互作用,因此石墨烯上施加了金属光栅结构.研究发现光栅结构能够对入射光进行动量补偿并且能够引起其下石墨烯中的电场强度产生很大程度增强,从而导致在该石墨烯结构中太赫兹等离激元和入射光发生强烈耦合而产生太赫兹等离极化激元,同时引起石墨烯光吸收的增强.希望本文能够加深对石墨烯光电特性的理解以及可以为基于石墨烯的太赫兹光电装置提供一定的理论依据.     

Tunable terahertz acoustic-phonon emission from monolayer molybdenum disulfide

The acoustic-phonon emission from monolayer molybdenum disulfide (ML-MoS₂) driven by a direct-current electric field is studied theoretically using the Boltzmann equation method. It is found that the Cerenkov emission of terahertz acoustic-phonons can be generated when a very weak electric field is applied to ML-MoS₂. The physical mechanisms of acoustic-phonon emission are analyzed from the perspective of condensed matter physics. The acoustic-phonon emission from ML-MoS₂ is also compared with those from graphene and GaAs. The results reveal that the frequencies of acoustic-phonons generated by ML-MoS₂ are between the frequencies of those generated from GaAs and graphene. The results of this work suggest that the ML-MoS₂ can make up for graphene and GaAs in respect of acoustic-phonon emission and be used in tunable hypersonic devices such as terahertz sound sources.