Composite fermions close to the one-half filling of the lowest Landau level revisited

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By strictly adhering to the microscopic theory of composite fermions (CFs) for the Landau-level filling fractions νₑ = p/(2 p + 1), we reproduce, with remarkable accuracy, the surface-acoustic-wave (SAW)-based experimental results by Willett and co-workers concerning two-dimensional electron systems with νₑ close to 1/2. Our results imply that the electron band mass mb, as distinct from the CF mass m*, must undergo a substantial increase under the conditions corresponding to νₑ close to 1/2. We further establish that a finite mean-free path ℓ₀ is essential for the observed linearity of the longitudinal conductivity σxx(q) as deduced from the SAW velocity shifts.