title: Dispersion of the excitations of fractional quantum Hall States.
abstract: The rich correlation physics in two-dimensional (2D) electron systems is governed by the dispersion of its excitations. In the fractional quantum Hall regime, excitations involve fractionally charged quasi particles, which exhibit dispersion minima at large momenta referred to as rotons. These rotons are difficult to access with conventional techniques because of the lack of penetration depth or sample volume. Our method overcomes the limitations of conventional methods and traces the dispersion of excitations across momentum space for buried systems involving small material volume. We used surface acoustic waves, launched across the 2D system, to allow incident radiation to trigger these excitations at large momenta. Optics probed their resonant absorption. Our technique unveils the full dispersion of such excitations of several prominent correlated ground states of the 2D electron system, which has so far been inaccessible for experimentation.
authors.affiliation: Max Planck Institute for Solid State Research, D-70569 Stuttgart, Germany.
authors.forename: Igor V
authors.initials: IV
authors.lastname: Kukushkin
authors.forename: Jurgen H
authors.initials: JH
authors.lastname: Smet
authors.forename: Vito W
authors.initials: VW
authors.lastname: Scarola
authors.forename: Vladimir
authors.initials: V
authors.lastname: Umansky
authors.forename: Klaus
authors.initials: K
authors.lastname: von Klitzing