Effect of gauge-field interaction on fermion transport in 2D

Igor Gornyi

Forschungszentrum Karlsruhe, Germany

We consider the quantum corrections to the conductivity of fermions interacting via a Chern-Simons gauge field, and concentrate on the Hartree-type contributions. In the realistic case of strong coupling to the gauge field, an infinite summation of higher-order terms is necessary, including both the virtual (renormalization) and real (dephasing) processes. At intermediate temperatures, the T-dependence of the conductivity is determined by the Hartree correction, so that the conductivity increases with lowering T. At low temperatures, the negative exchange contribution becomes dominant, yielding localization in the limit of zero T. We further discuss dephasing effects and show that the dephasing rates are of the order of T, owing to the interplay of inelastic scattering and renormalization. On the other hand, the dephasing length is anomalously short (much shorter than the thermal length). For the case of composite fermions with long-range Coulomb interaction, the gauge field propagator is less singular. The resulting Hartree correction has the usual sign and temperature-dependence, and for realistic conductances is overcompensated by the negative exchange contribution due to the gauge-boson and scalar parts of the interaction.