Zusammenfassung
We study the AC properties of a two-dimensional electron gas in high-mobility samples at half-filling of the lowest Landau level within the framework of the composite-fermion (CF) theory. We have shown that the low-frequency behavior of the AC conductivity σxx(ω) in the presence of smooth disorder is governed by quasiclassical memory effects that are related to return processes neglected in ...
Zusammenfassung
We study the AC properties of a two-dimensional electron gas in high-mobility samples at half-filling of the lowest Landau level within the framework of the composite-fermion (CF) theory. We have shown that the low-frequency behavior of the AC conductivity σxx(ω) in the presence of smooth disorder is governed by quasiclassical memory effects that are related to return processes neglected in Boltzmann transport theory. We have demonstrated that the fictitious random magnetic field acting on CFs strongly enhances this anomalous contribution to σxx(ω); specifically, the return-induced correction to shows a pronounced cusp ∝|ω|. This anomaly is of quasiclassical origin and dominates (compared to quantum corrections ) in a wide frequency range, provided kFd⪢1, where kF is the CF Fermi wave vector, d the correlation radius of disorder. The prefactor of the |ω| term is proportional to d/l (l is the mean free path of the CFs).
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