Drude conductivity of Dirac fermions in graphene

作者：Jason Horng, Chi-Fan Chen, Baisong Geng, Çağlar Girit, Yuanbo Zhang, Zhao Hao, Hans A. Bechtel, Michael C. Martin, Alex K. Zettl, Michael F. Crommie, Y. Ron Shen, Feng Wang · 发表于：Physical Review B · 年份：2011 · DOI：10.1103/physrevb.83.165113 · 被引用次数：556 · 研究领域：Graphene research and applications、Topological Materials and Phenomena、Quantum and electron transport phenomena

Electrons moving in graphene behave as massless Dirac fermions, and they exhibit fascinating low-frequency electrical transport phenomena. Their dynamic response, however, is little known at frequencies above one terahertz (THz). Such knowledge is important not only for a deeper understanding of the Dirac electron quantum transport, but also for graphene applications in ultrahigh-speed THz electronics and infrared (IR) optoelectronics. In this paper, we report measurements of high-frequency conductivity of graphene from THz to mid-IR at different carrier concentrations. The conductivity exhibits Drude-like frequency dependence and increases dramatically at THz frequencies, but its absolute strength is lower than theoretical predictions. This anomalous reduction of free-electron oscillator strength is corroborated by corresponding changes in graphene interband transitions, as required by the sum rule.