FRACTIONAL QUANTUM HALL-EFFECT MEASUREMENTS AT ZERO G-FACTOR

Fractional quantum Hall effect energy gaps have been measured as a fun ction of Zeeman energy. The gap at v = 1/3 decreases as the g factor i s reduced by hydrostatic pressure. This behavior is similar to that at v = 1 and shows that the excitations are spinlike. At small Zeeman en ergy, the excitation is consistent with the reversal of 3 spins and ma y be interpreted as a small composite Skyrmion. At 20 kbar, where g ha s changed sign, the 1/3 gap appears to increase again.