第46回 原研・兵県大合同コロキウム

日時: 平成20年7月17日(木) 15:00〜
Date and time: 17th July (Thu.) 15:00〜
場所: SPring-8, 萌光館
Place: SPring-8, "HOUKOUKAN" seminar room
Title: Quantum transport phenomena of massless Dirac fermions in graphene
講演者: 野村 健太郎 氏 (東北大学理学部)
Speaker: Dr. Kentaro Nomura (Tohoku University)
Abstract:

Graphene is a two-dimensional carbon material with a honeycomb lattice structure. Originating to its Dirac-like spectrum, quantum transport phenomena of graphene reveal exotic behaviors, as seen in the localization problems and the quantum Hall effects.[1] We have undertaken numerical studies of the conductivity of disordered two-dimensional massless Dirac fermions.[2,3,4,5] The beta function of the Dirac hamiltonian subject to a random scalar potential shows novel behavior which is qualitatively different from that of the spin-orbit coupling model, although they belong to same symmetry class.[4] We provide an argument based on the spectral flows under twisting boundary conditions, which shows that none of states of the massless Dirac Hamiltonian can be localized. General types of disorder are also taken into account to address the observed minimal conductivity at the charge neutral Dirac point. In a perpendicular magnetic field, anomalous quantum Hall effect realizes. We show that the quantum Hall phases with σxy=± ½ [e2/h] (per valley and per spin) survive in the limit of weak magnetic fields, when intra-valley scattering dominates.[5]