Department of Physics
Condensed Matter Seminar

Graphene, a single atomic sheet of graphite, is a monolayer of carbon atoms arranged in a hexagonal lattice. The low-energy band structure of graphene can be approximated as two opposite cones located at two inequivalent Brillouin zone corners, and the point where the apexes of these two cones touch is called Dirac point. Near the Dirac point, where energies of electrons and holes are degenerate, the 2D energy dispersion relation is linear; electrons/holes behave like relativistic, massless Dirac particles. This band structure of graphene differs radically from the parabolic bands common to all previous 2D systems, leading to intriguing new phenomena. In this talk, I focus on two projects related to graphene that complement each other: magneto-transport measurements in high magnetic fields, and infrared optical studies of graphene. In the transport experiments, we investigate the distinctive half-integer quantum Hall effect in graphene and its Landau level (LL) splittings in the extreme quantum limit [1-3]. In the infrared experiments, we perform infrared transmission measurements in graphene at selected LL fillings [4,5]. Resonances between hole LLs and electron LLs (intraband transitions), as well as resonances between hole and electron LLs (interband transitions) are resolved. For both projects, we argue that manybody correlation of effectively massless Dirac Fermions provides considerable contributions to our experimental results