Spontaneous stripe order at certain even-denominator fractions in the lowest Landau level

An understanding of the physics of half or quarter 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 in this work 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, 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.