Fractional Quantum Hall Effect Measurements at Zero g-Factor

Fractional quantum Hall effect energy gaps have been measured in GaAs/GaAlAs heterojunctions as a function of Zeeman energy, which is varied by applying hydrostatic pressure up to 20 kbar. The gap at v=1/3 decreases with pressure until the g-factor changes sign when it again increases. The behavior is similar to that seen at v=1 and shows that excitations from the 1/3 ground state can be spin-like in character. At small Zeeman energy, the excitation appears to consist of 3 spins and may be interpreted as a small composite skyrmion.