# Regensburg 2013 – wissenschaftliches Programm

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# MM: Fachverband Metall- und Materialphysik

## MM 15: Poster Session

### MM 15.26: Poster

### Montag, 11. März 2013, 18:00–20:00, Poster E

**Coulomb drag in monolayer 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 MLG using Boltzmann kinetic theory, taking into the two relevant modes for both particles and holes in each layer. In the Fermi liquid (FL) regime of monolayer graphene (MLG), 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 Dirac theory of MLG. 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. In the very clean limit, when the impurity density reaches zero, the drag resistivity assumes an universal finite value, although the individual conductivities diverge.