Signatures of a Wigner crystal in the chemical-potential evolution of a two dimensional electron system

We investigate the chemical-potential evolution of a two-dimensional electron system (2DES) exposed to a perpendicular magnetic field a function of density. By using a bilayer system, changes in the chemical potential of one 2DES are determined from the density variation induced in a second close-by 2DES. At high magnetic elds, the chemical-potential evolution within a quantum Hall plateau regime exhibits two anomalies symmetrically located around an integer filling factor 1 or 2. We attribute these anomalies to the formation of a 2D Wigner crystal and of quasi-particles.