Regensburg 2013 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 26: Graphene - Electronic Properties and Transport 2 (jointly with DS, HL, MA, and O)

TT 26.4: Talk

Tuesday, March 12, 2013, 10:15–10:30, H17

Coulomb drag in bilayer graphene — •Jonathan Lux — Institut für theoretische Physik, Universität zu Köln

Coulomb drag measurements provide an interesting possibility to study interaction effects between two adjacent layers. If a current is driven in one of the layers, called the active layer, via Coulomb interaction, momentum can be transferred to the other layer, called the passive layer. This can induce a voltage drop in the passive layer, which can be measured. The ratio of the voltage drop in the passive layer and the current in the active layer is called the drag resistance.

We have calculated the drag resistivity in bilayer graphene (BLG) using Boltzmann kinetic theory, taking into the relevant mode for both particles and holes in each layer. In the Fermi liquid (FL) regime of BLG, the drag resistivity is, up to numerical prefactors, identical to the one in the 2 dimensional electron gas, and independent of the impurity configuration.

Near charge neutrality, Coulomb interaction is able to relax the current, due to the particle--hole symmetry of the low energy theory of BLG. This defines a new regime, which is not accessible in FLs. We found that here the result depends on the ratio of the scattering times of Coulomb and impurity scattering. Special attention is paid to the differences and similarities to the drag in monolayer graphene.