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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. Wegscheider21Institut 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

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