The theory of optical effects in hydrogenated graphene (graphane) in terahertz and infrared range is developed, including the analysis of complex conductivity, reflection coefficient for graphane on a substrate and dispersion of surface plasmon-polaritons. The calculations are based on quite simple analytical approximation of graphane band structure in the vicinity of Gamma-point and on the modified model of quantum coherence relaxation. Comparison of the obtained theoretical results with corresponding experimental data can be used both for the determination of graphane characteristics (Fermi level, relaxation rate etc.) and for the investigation of potential applications of this material in the design of new optical elements.
Recent studies on excitons in two-dimensional materials have been widely conducted for their potential usages for novel electronic and optical devices. Especially, sophisticated manipulation techniques of quantum degrees of freedom of excitons are demanded. In this paper we propose a technique of forming an optical dipole trap for excitons in graphane, a two-dimensional wide gap semiconductor, based on first principles calculations. We develop a first principles method to evaluate the exciton transition dipole matrix and combine it with the density functional theory and GW+BSE calculations. We…
Optical spin injection in graphane and fluorographene
Universidad de Ciencias y Artes de Chiapas（恰帕斯艺术与科学大学）；Instituto de Investigación e Innovación en Energías Renovables（可再生能源研究与创新中心）；Centro Universitario de la Ciénega, Universidad de Guadalajara（瓜达拉哈拉大学锡内加大学中心）；Universidad Politécnica de Chiapas（恰帕斯理工大学）；Universidad Autónoma de Occidente (UAdeO)（西方自治大学）；Universidad Politécnica de Tapachula（塔帕丘拉理工大学）
We investigate the effect of Rashba spin-orbit coupling (SOC) on the optoelectronic properties of n- and p-type monolayer MoS2. The optical conductivity is calculated within the Kubo formalism. We find that the spin-flip transitions enabled by the Rashba SOC result in a wide absorption window in the optical spectrum. Furthermore, we evaluate the effects of the polarization direction of the radiation, temperature, carrier density, and the strength of the Rashba spin-orbit parameter on the optical conductivity. We find that the position, width, and shape of the absorption peak or absorption wind…
The strength of light-matter interaction is of central importance in photonics and optoelectronics. For many widely studied two-dimensional semiconductors, such as MoS2, the optical absorption due to exciton resonances increases with thickness. However, here we will show, few-layer black phosphorus exhibits an opposite trend. We determine the optical conductivity of few-layer black phosphorus with thickness down to bilayer by infrared spectroscopy. On the contrary to our expectations, the frequency-integrated exciton absorption is found to be enhanced in thinner samples. Moreover, the continuu…
Gate-Variable Mid-Infrared Optical Transitions in a $(Bi_{1-x}Sb_x)_2Te_3$ Topological Insulator
我们报告了静电门控拓扑绝缘体的中红外光谱测量，其中我们观察到随着门控移动费米能级，（Bi 1-xSbx）2 Te 3薄膜的透射率和反射率发生百分之几的调制。采用外延剥离法将拓扑绝缘体薄膜从红外吸收SrTiO 3生长衬底大面积转移到热氧化硅衬底上，测量了栅控（Bi 1-xSbx）2 Te 3薄膜的红外透射率。我们将这些光学实验与传输测量和角度分辨光电子能谱相结合，以确定所观察到的光谱调制作为门驱动的光谱权重之间的批量和拓扑表面通道和带间和带内通道的转移。我们开发了一个模型的门控（Bi 1-xSbx）2 Te 3的复介电常数，并找到一个很好的匹配我们的实验数据。这些结果开辟了层状拓扑绝缘体材料作为一个新的候选人可调谐红外光学的路径，并突出了体和自旋极化表面制度之间切换拓扑光电现象的可能性。
When two-dimensional electron gases (2DEGs) are exposed to magnetic field, they resonantly absorb electromagnetic radiation via electronic transitions between Landau levels (LLs). In 2DEGs with a Dirac spectrum, such as graphene, theory predicts an exceptionally high infrared magneto-absorption, even at zero doping. However, the measured LL magneto-optical effects in graphene have been much weaker than expected because of imperfections in the samples available so far for such experiments. Here we measure magneto-transmission and Faraday rotation in high-mobility encapsulated monolayer graphene…
