单层石墨烯是在室温下能存在的二维电子气，由于其线性色散关系与传统二维电子气相区别，在光、电、磁等多方面(如室温量子霍尔效应、高迁移率、高热导率和最小电导率等)表现出不同的输运行为，使其在微电子和透明导电膜方面有巨大的应用前景。采用在无规相近似下的介电函数来分析两类二维电子气系统中的光电导谱的异同。结果表明，包含两支能谱的体系中带间的跃迁对光电导起主要贡献，而两体系中带内的跃迁对光导的贡献很小。光谱的形状依赖于费米能级和由散射引起的能级展宽。当入射光的能量远高于2EF时，光电导趋于一常数，与实验结果一致。

Monolayer graphene is a two dimensional electron gas (2DEG) which is obtained at room temperature. The optical, electrical and magnetic transport properties (e.g., room temperature quantum Hall effect, high mobility, high thermal conductivity, minimum conductivity, etc.) in graphene represent different transport behaviors for the difference of it′s linear dispersion relation and that of traditional 2DEG. This graphene material has huge potential applications in microelectronics and transparent conductive films. The dielectric function under the random phase approximation (RPA) is employed to evaluate the optical conductivity in the traditional 2DEG and the graphene system. It is found that the main optical conductivity is induced by the inter-band transition with two-branch energy spectrum, while the contribution by the intra-band transition is very small. The shape of the conductivity spectrum depends on the Fermi energy and the broadening width which is determined by the scattering mechanism. When the optical energy is larger than 2EF, the optical conductivity tends to a constant which is consistent with the experimental result.