Dresden 2009 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 9: Poster 1
HL 9.120: Poster
Monday, March 23, 2009, 14:30–17:00, P2
Gap measurements at filling factors 1/3 and 2/5 in the FQHE regime — •Oliver Gerberding1, Lina Bockhorn1, Annelene F. Dethlefsen1,2, Werner Wegscheider3, and Rolf J. Haug1 — 1Institut für Festkörperphysik, Leibniz Universität Hannover — 2Centre for Atom Optics and Ultrafast Spectroscopy, Faculty of Engineering and Industrial Science, Swinburne University of Technology — 3Institut für Experimentelle und Angewandte Physik, Universität Regensburg
We study the fractional Quantum-Hall effect in high mobility twodimensional electron systems (2DES). The Hall geometries are created by photolithography on a GaAs/GaAlAs heterostructure containing a 2DES.
The activation gaps of the fractional Quantum-Hall state at constant filling factors 1/3 and 2/5 have been measured as a function of a perpendicular magnetic field B. The mobility and the density of electrons are manipulated by using a topgate. For a given density of electrons we study the Shubnikov-de Haas oscillations for different temperatures to extract the activation energies.
For several filling factors we find an astonishing linear dependence for small magnetic fields and a cross over to square root dependence for high magnetic fields.