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Using acoustic method we study dependences of transverse AC conductance, $sigma (omega)$, on magnetic field, temperature and the amplitude of AC electric field in a wide (75 nm) quantum well (QW) structure focusing on the vicinity of the filling factor $ u =1/2$. Measurements are performed in the frequency domain 30-307 MHz and in the temperature domain 20-500 mK. Usually, in wide QW structures closely to $ u =1/2$ the fractional quantum Hall effect (FQHE) regime is realized at some parameters of the sample. However, in our structure, at $ u =1/2$ it is a compressible state corresponding to gas of composite fermions which is observed. This is confirmed by apparent frequency independence and weakly decreasing temperature dependence of $mathrm{Re}, sigma(omega)$. Comparing the dependences of this quantity on temperature and power of the acoustic wave we conclude that the observed nonlinear behavior of the conductance is compatible with heating of the composite fermions by the acoustic wave. For comparison, we also study the vicinity of $ u = 3/2$ where the FQHE regime is clearly observed.
In bilayer quantum Hall systems at filling fractions near nu=1/2+1/2, as the spacing d between the layers is continuously decreased, intra-layer correlations must be replaced by inter-layer correlations, and the composite fermion (CF) Fermi seas at l
By simultaneous measurements of the attenuation and velocity of surface acoustic waves propagating in proximity to a high-quality GaAs quantum well we study the complex AC conductance of the two-dimensional electron system. Focusing on the vicinity o
The pairing of composite fermions (CFs), electron-flux quasi-particles, is commonly proposed to explain the even-denominator fractional quantum Hall state observed at $ u=5/2$ in the first excited ($N=1$) Landau level (LL) of a two-dimensional electr
Composite fermions in fractional quantum Hall (FQH) systems are believed to form a Fermi sea of weakly interacting particles at half filling $ u=1/2$. Recently, it was proposed (D. T. Son, Phys. Rev. X 5, 031027 (2015)) that these composite fermions
We have studied temperature dependence of both diagonal and Hall resistivity in the vicinity of $ u=1/2$. Magnetoresistance was found to be positive and almost independent of temperature: temperature enters resistivity as a logarithmic correction. At