Periodic Density Modulation Effects on a Correlated two-dimensional Composite Fermion System
We examine theoretically the effects caused by a periodic external potential on the correlated motion of a two-dimensional electron system under strong magnetic fields corresponding to a filling factor 1/2. To describe the resulting complex dynamics, we adopt a composite fermion approach and we determine in a two loop approximation the density-response function $K_{00}(\bfq,\omega)$ and the compressibility. We show explicitly that the long-wavelength limit of $K_{00}(\bfq,\omega)$ exhibits substantial anisotropic behavior induced by the modulation, and that the system tends to be incompressible in a direction orthogonal to the modulation as opposed to its response along the modulation.