ELECTRON CRYSTALLIZATION IN 2 DIMENSIONS

Electrons confined at the interface of a GaAs/GaAlAs heterojunction form a 2D quantum electron liquid. Under a strong magnetic field a phase transition to an electron (Wigner) solid takes place in the low filling factor regime of the Fractional Quantum Hall Effect (FQHE). We describe experimental evidence for such electron solid formation obtained both by radiofrequency (RF) study of the low-frequency collective excitations and by conductivity measurements. A finite-threshold electric field for DC conduction reflecting the electron crystallite pinning in the sample random potential is found associated to a small gap in the solid phase low-lying collective excitation branch. The nu = 1/5 FQHE liquid reenters the solid domain at low temperature.