2-DIMENSIONAL ELECTRONS NEAR A HALF-FILLED LANDAU-LEVEL

We propose an explanation of the recently observed transport anomaly at half-filling in terms of the quasisolid wave function of Chui, Hakim, and Ma. The energy of this state is equal to -0.467, quite close to the extrapolated value from the finite-cluster calculation of -0.469 by Fano et al. At low temperatures, the phonon develops a gap of magnitude 0.393/2 for 0.5. This is interpreted as the origin for the dip in . On the other hand, there exists a gapless mode corresponding to a vacancy-interstitial excitation. Thus never reaches zero completely, as is experimentally observed. The quasisolid wave function can also be written at filling factors other than 1/2. Thus the Hall coefficient is not pinned, consistent with the absence of a sharp Hall plateau. © 1990 The American Physical Society.