Using Composite Fermions to Probe a Wigner Solid in 2D Hole Systems

We have studied a GaAs double-quantum-well structure that hosts an interacting, bilayer two-dimensional hole system with a large density difference between the two layers. At very low temperatures and large perpendicular magnetic field, we expect the two layers to exhibit distinct many-body states of holes: The high-density layer develops a Fermi sea of composite fermions when its last Landau Level is half-filled, while the holes in the low-density layer in the same magnetic field range are at very small fillings and should condense into a Wigner crystal. Via measuring the magneto-resistance of the bilayer system, we monitor signatures of the Wigner crystallization and melting