title: Terahertz Dynamics of a Topologically Protected State: Quantum Hall Effect Plateaus near the Cyclotron Resonance of a Two-Dimensional Electron Gas.
abstract: We measure the Hall conductivity of a two-dimensional electron gas formed at a GaAs/AlGaAs heterojunction in the terahertz regime close to the cyclotron resonance frequency using highly sensitive Faraday rotation measurements. The sample is electrically gated, allowing the electron density to be changed continuously by more than a factor of 3. We observe clear plateaulike and steplike features in the Faraday rotation angle vs electron density and magnetic field (Landau-level filling factor) even at fields or frequencies very close to cyclotron resonance absorption. These features are the high frequency manifestation of quantum Hall plateaus-a signature of topologically protected edge states. We observe both odd and even filling factor plateaus and explore the temperature dependence of these plateaus. Although dynamical scaling theory begins to break down in the frequency region of our measurements, we find good agreement with theory.
authors.affiliation: Department of Physics, University at Buffalo, The State University of New York, Buffalo, New York 14260, USA.
authors.forename: A V
authors.initials: AV
authors.lastname: Stier
authors.affiliation: Department of Physics, University at Buffalo, The State University of New York, Buffalo, New York 14260, USA.
authors.forename: C T
authors.initials: CT
authors.lastname: Ellis
authors.affiliation: Department of Physics, University at Buffalo, The State University of New York, Buffalo, New York 14260, USA.
authors.forename: J
authors.initials: J
authors.lastname: Kwon
authors.affiliation: Department of Physics, University at Buffalo, The State University of New York, Buffalo, New York 14260, USA.
authors.forename: H
authors.initials: H
authors.lastname: Xing
authors.affiliation: Department of Physics, University at Buffalo, The State University of New York, Buffalo, New York 14260, USA.
authors.forename: H
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Department of Physics, University at Buffalo, The State University of New York, Buffalo, New York 14260, USA.
authors.forename: D
authors.initials: D
authors.lastname: Eason
authors.affiliation: Department of Physics, University at Buffalo, The State University of New York, Buffalo, New York 14260, USA.
authors.forename: G
authors.initials: G
authors.lastname: Strasser
authors.affiliation: Department of Physics, University of Tokyo, Hongo, Tokyo 113-0033, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Morimoto
authors.affiliation: Department of Physics, University of Tokyo, Hongo, Tokyo 113-0033, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Aoki
authors.affiliation: Department of Physics, University at Buffalo, The State University of New York, Buffalo, New York 14260, USA.
authors.forename: H
authors.initials: H
authors.lastname: Zeng
authors.affiliation: Department of Physics, University at Buffalo, The State University of New York, Buffalo, New York 14260, USA.
authors.forename: B D
authors.initials: BD
authors.lastname: McCombe
authors.affiliation: Department of Physics, University at Buffalo, The State University of New York, Buffalo, New York 14260, USA.
authors.forename: J
authors.initials: J
authors.lastname: Cerne