PHYSICS/BK21 SEMINAR (08/10/08)
관련링크
본문
"“Magnetotransport of Graphene Devices in
Edgeless Corbino Geometry ”
Speaker : Dr. Dong-Hun Chae [Max-Planck-Institute, Germany]
Place : Physics Conference Room (Science Bldg, 3-201)
Date & Time : Oct, 8(Wed) 4:00 ~ 5:00 pm
Abstract
We present electronic transport properties of graphene devices in a Corbino geometry. For this (and only this) sample topology, the classical Drude picture predicts a quadratic dependence of the inverse conductivity on the applied external magnetic field. Our key observation is a non-quadratic B-field dependence of the inverse conductivity near the charge neutrality point. We argue that the non-quadratic behavior is attributed to the characteristic square root dependence of the magnetic field for the cyclotron frequency of graphene near the Dirac point. We have also investigated the scattering mechanism by experimentally determining the transport relaxation time as a function of carrier density. In addition, motivated by planar graphene pn-junctions, edgeless graphene bipolar junctions are realized in a Corbino geometry. In the ordinary pn-junction, observed fractional conductance plateaus in the quantum Hall regime were explained in terms of the equilibration of edge channels near the junction, leading to a classical serial connection of ohmic conductors. Unlike the planar pn-junction, transport in high magnetic field is understood by quantum Hall effect without the edge channels and equilibration at the interface. That is, if either of two regions, which have different carrier densities and/or types, is in quantum Hall regime, the transport through both regions is pinched off accordingly.
Contact Person : Prof. Hu-Jong Lee(054-279-2072, hjlee@postech.ac.kr)
"
Edgeless Corbino Geometry ”
Speaker : Dr. Dong-Hun Chae [Max-Planck-Institute, Germany]
Place : Physics Conference Room (Science Bldg, 3-201)
Date & Time : Oct, 8(Wed) 4:00 ~ 5:00 pm
Abstract
We present electronic transport properties of graphene devices in a Corbino geometry. For this (and only this) sample topology, the classical Drude picture predicts a quadratic dependence of the inverse conductivity on the applied external magnetic field. Our key observation is a non-quadratic B-field dependence of the inverse conductivity near the charge neutrality point. We argue that the non-quadratic behavior is attributed to the characteristic square root dependence of the magnetic field for the cyclotron frequency of graphene near the Dirac point. We have also investigated the scattering mechanism by experimentally determining the transport relaxation time as a function of carrier density. In addition, motivated by planar graphene pn-junctions, edgeless graphene bipolar junctions are realized in a Corbino geometry. In the ordinary pn-junction, observed fractional conductance plateaus in the quantum Hall regime were explained in terms of the equilibration of edge channels near the junction, leading to a classical serial connection of ohmic conductors. Unlike the planar pn-junction, transport in high magnetic field is understood by quantum Hall effect without the edge channels and equilibration at the interface. That is, if either of two regions, which have different carrier densities and/or types, is in quantum Hall regime, the transport through both regions is pinched off accordingly.
Contact Person : Prof. Hu-Jong Lee(054-279-2072, hjlee@postech.ac.kr)
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