Dmitry Abanin Department of Physics, Massachusetts Institute of Technology, Cambridge, MA Condensed Matter Theory Seminar, Monday, 1/14/2008

Abstract: In the first part of the talk, I will focus on Quantum Hall Effect (QHE) in graphene p-n junctions, which has been recently demonstrated experimentally. I will explain the observed conductance quantization which is fractional in the bipolar regime and integer in the unipolar regime in terms of QHE edge modes propagating along and across the p-n interface. In the bipolar regime the electron and hole modes can mix at the p-n boundary, leading to current partition and quantized shot noise plateaus similar to those of conductance, while in the unipolar regime transport is noiseless. In the second part of the talk, I will discuss unusual nature of nu = 0 QHE state in graphene and show that electron transport in this regime may be dominated by counter-propagating edge states. Such states, intrinsic to massless Dirac quasiparticles, manifest themselves in a smeared plateau in the Hall conductivity and large longitudinal resistivity rho_xx~h/e^2, in contrast to rho_xx behavior in the standard QHE.

pdf file of the talk