Regensburg 2004 – scientific programme
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HL: Halbleiterphysik
HL 22: Transport im hohen Magnetfeld/Quanten-Hall-Effekt
HL 22.1: Talk
Tuesday, March 9, 2004, 15:15–15:30, H14
Phonon spectroscopy in the fractional quantum Hall effect regime — •F. Schulze-Wischeler1, F. Hohls1, U. Zeitler1,2, R. J. Haug1, D. Reuter3, and A. D. Wieck3 — 1Institut für Festkörperphysik, Universität Hannover, Appelstraße 2, D-30167 Hannover, Germany — 2High Field Magnet Laboratory, NSRIM, University of Nijmengen, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands — 3Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, Universitätsstraße 150, 44780 Bochum, Germany
At low temperatures the energies und wavelength of phonons become comparable to the typical energies- und length scales of two-dimensional electron systems (2DESs). So they can couple efficiently to 2DESs and make collective excitations. We have measured the absorption of ballistic non-equilibrium phonons by a 2DES in the fractional quantum Hall effect (FQHE) regime. With phonon spectroscopy we can measure the specific heat of 2DESs and energy gaps unaffected by disorder on length scales larger than phonon wavelength (in contrary to transport experiments). For various filling factors and electron densities energy gaps in the FQHE are measured. A comparison with theory gives insight into the interesting nature of these collective states.