Thermodynamic measurements in a fractional quantum Hall effect and the composite-fermion approach

A quantitative comparison of the magnetocapacitance measurements on high-quality samples in the fractional quantum Hall effect with the composite-fermion approach has been performed. For this comparison, the relation between the electron chemical potential μ _e and quasi-particle spectrum has been derived. The effect of the temperature T has been calculated in the two-level approximation. The calculation quantitatively describes the decrease in the measured chemical-potential jump at filling factors of ν = 1/3, 2/5 with increasing T. In the compressible range 1/3 < ν < 2/5, the slope of the temperature dependence dμe/dν(T) is also in agreement with the calculation. The discrepancy of the composite-fermion approach with the experimental data is in the incorrectly predicted gaps and their dependence on the denominator of a fraction.