Berlin 2005 – scientific programme
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HL: Halbleiterphysik
HL 53: Transport im hohen Magnetfeld/Quanten-Hall-Effekt
HL 53.2: Talk
Tuesday, March 8, 2005, 15:15–15:30, TU P270
Activation gaps of different fractional quantum Hall states — •A.F. Dethlefsen1, F. Schulze-Wischeler1, R.J. Haug1, and W. Wegscheider2 — 1Institut für Festkörperphysik, Universität Hannover, D-30167 Hannover — 2Institut für Angewandte und Experimentelle Physik, Universität Regensburg, D-93040 Regensburg
The activation gap Δ of the fractional quantum
Hall states at constant fillings ν = 2/3, 2/5 and 1/3 has been
measured as a function of the perpendicular magnetic field B for various
electron densities. For each density we measured the temperature
dependence of the resistivity ρxx(T). We observe
activated transport ρxx ∝
exp(−Δ/2T). A linear dependence of Δ on B is
observed for ν=2/3 and 2/5 while approaching the spin polarization
transition for both fillings with different slopes. This allows a direct
measurement of the g-factor of composite fermions (CFs).
To obtain a deeper insight in the dependence of the activation gap on the
electronic filling factor we perform further measurements at filling
factor ν =1/3 in a wider magnetic field range, where spin-effects
should only play a role at small magnetic fields.
[1] F. Schulze-Wischeler, E. Mariani, F. Hohls and R. J. Haug, Phys. Rev. Lett. 92, 156401 (2004