Topological transition of graphene from quantum Hall metal to quantum Hall insulator – Prof. XiangRong Wang
Date: Fri. May 17th, 2013, 12:30 pm-1:30 pmLocation: Rockefeller 221
In this talk, I will first review the basic electronic properties of graphene. In particular, I will explain why the recently observed insulating phase of graphene at charge neutrality point in high magnetic field quantum Hall (QH) experiments is a big surprising. Then I will present a simple single-particle theory for this intriguing finding. We show that the magnetic field driven Peierls-type lattice distortion (due to the Landau level degeneracy) and random bond fluctuations compete with each other, resulting in a transition from a QH-metal state at relative low field to a QH-insulator state at high enough field at the charge neutrality point. The critical field that separates QH-metal from QH-insulator depends on the bond fluctuation. The picture explains well why the field required for observing the insulating phase is lower for a cleaner sample.