•Eros Mariani¹, Maura Sassetti² und Bernhard Kramer^1
1I Institut fuer Theoretische Physik, Universitaet Hamburg, Jungiusstrasse 9, D-20355 Hamburg, Germany
²Dipartimento di Fisica, INFM, Universita' di Genova, Via Dodecaneso 33, I-16146 Genova, Italy

The degree of spin polarization g_e of the FQHE ground state at fixed filling factors n is analyzed within a mean field approximation for spinful composite fermions (CF). By varying the magnetic field B several phase transitions between differently polarized ground states are predicted, in excellent agreement with recent experimental measurements [1]. Including spin-orbit coupling between different CF Landau levels yields the zero temperature smoothening of g_e around the phase transition points. Additional semiquantitative predictions for the activation gap as a function of B are made. These are in good agreement with analogous experimental studies at n = \frac23 and \frac85 [2,3].

[