摘要:
通过有效哈密顿量求解了单层MoS2低能量区的电子薛定谔方程,分析得出电子能量本征值以及波函数、电子态密度以及电子间的屏蔽长度.发现电子能带分裂成两支导带和两支价带,并且其能带是准线性的.MoS2的电子间的屏蔽长度非常大,高达108 cm-1.利用费曼图形自洽方法,在无规相近似的基础上研究了单层二硫化钼电子系统的多体相互作用产生的等离激元.研究发现二硫化钼系统由于自旋的劈裂使得导带中存在两支自旋频率不同的等离激元,该元激发的特征与单层石墨烯和传统二维电子气的等离激元对波矢q的依赖关系是一样的,激发频率都正比于q1/2,并且随着电子浓度的增加激发频率增大.由于其准线性的能量色散关系,该系统等离激元的频率与电子浓度的变化关系非常不同于石墨烯和二维电子气的关系.自旋-轨道耦合对单层二硫化钼的能带结构和电子性质有重要的影响.研究发现,通过调控二硫化钼系统的电子浓度可以有效地调节该系统两支等离激元的频率.研究结果对理解二硫化钼的电子结构和性质,以及开发二硫化钼为基础的等离子器件有重要的研究和参考价值.
Abstract:
We obtain the energy eigenvalues and wave functions of the single layer molybdenum disulfide by using an effective Hamiltonian. Moreover, the density of states and high electron-electron screening length up to 108 cm-1 are also evaluated based on the dielectric function of MoS2. It is shown that the quasi-linear energy bands split off due to the spin-orbit couplings. Plasmons in such a system are investigated theoretically within diagrammatic self-consistent field theory. In the random phase approximation, it is found that two plasma spectra can be produced via intra band transitions induced in conduction bands in monolayer MoS2 because of splitting off. The plasma spectrum frequency increases with increasing wave-vector q and electron density. It is found that the two plasmon modes induced by the spin intra-subband transitions are acoustic-like and depend strongly on wave-vector q. We find that the plasma spectrum is very different from those of graphene and two-dimensional electron gas due to the quasi-linear dispersion and spin-orbit couplings in single layer MoS2. Moreover, the plasmon frequency can be effectively controlled through changing the doping electron density. Our results exhibit some interesting features which can be utilized to realize the plasmonic devices based on the single layer MoS2.
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