Stripe Formation in the Fractional Quantum Hall Regime

An understanding of the physics of the half-filled lowest Landau level has been achieved in terms of a Fermi sea of composite fermions, but the nature of the state at other even-denominator fractions has remained unclear. We investigate theoretically Landau level fillings of the form nu = (2n + 1)/(4n + 4), which correspond to composite-fermion fillings nu* = n + 1/2. By considering various plausible candidate states with complete spin polarization, we rule out the composite-fermion Fermi sea and paired composite-fermion state at these filling factors, and predict that the system phase separates into stripes of n and n + 1 filled Landau levels of composite fermions.