Influence of spin on the activation energies at image

The activation energy Δ of the fractional quantum Hall state at constant filling factor View the MathML source and also at View the MathML source and View the MathML source has been measured as a function of the perpendicular magnetic field B while modulating the electron density via a top gate. At small magnetic fields we observe a linear increase of Δ with the magnetic field. The slope of Δ vs. B allows us to directly extract the composite fermion g-factor.