Graphene Photonics || Optoelectronic Properties

摘要： In the preceding chapter, the surface optical conductivity eσeωT of graphene contributed by interband transitions was considered, which characterizes the optical response of graphene in the high-frequency region and has a real part given by (3.106) when the relaxation rate is taken to be zero by ignoring the finite relaxation times of the states involved in the transitions. We find by using this surface optical conductivity that monolayer graphene has an approximately constant absorbance of about 2.3 percent in the optical spectral region. However, in the low-frequency region, the surface optical conductivity eσeωT obtained in the preceding chapter is not valid. For example, if we set ω ? 0 for eσe0T to find the DC surface conductivity, we find that eσe0T is also zero, which is inconsistent with the DC surface conductivity obtained in Chapter 2. The discrepancy comes from the fact that eσeωT given in the preceding chapter only accounts for interband absorption of photons with electrons making transitions from a valence band to a conduction band, whereas the DC surface conductivity given in Chapter 2 is solely contributed by the intraband transitions of charge carriers within a valence band or within a conduction band.