OBSERVATION OF THE FRACTIONAL QUANTUM HALL-EFFECT IN GAAS-(GA,AL)AS QUANTUM-WELL STRUCTURES

We report the observation of the fractional quantum Hall effect in single GaAs-(Ga,Al)As quantum well structures with well widths of 102 angstrom and 68 angstrom. In both samples we have observed a strong v = 4/3 fraction in both the longitudinal resistivity rho(xx) and the Hall resistivity rho(xy). The surprising result in our data (in comparison with the FQHE in conventional single heterojunctions) is that the 5/3 is heavily suppressed or possibly absent. In a tilted magnetic field the energy gap of 4/3 depends only on the perpendicular field. We associate this difference between our samples and the conventional heterojunctions with the energy (well width) dependence of the Lande g* factor and the influence of the Zeeman energy on the (partially) spin-polarized energy levels and hence the activation energies.