EFFECT OF VALENCE-BAND STRUCTURE ON THE FRACTIONAL QUANTUM HALL-EFFECT OF 2-DIMENSIONAL HOLE SYSTEMS

We have studied the effect of the valence band structure on the fracti onal quantum Hall effect (FQHE) of two-dimensional hole systems (2D HS ) in a symmetrically modulation-doped quantum well (QW). While keeping the hole density constant, we used front and back gates to vary the v alence band structure in situ by changing the QW potential symmetry. T he remarkable transitions we observed in the FQHE at v = 4/3 and 7/5 h ad a striking resemblance to the spin transitions reported for tilted- field experiments. We show that the effective g-factor determining the spin configuration of 2D HS in the FQHE is not a material-specific va lue, but reflects the valence band structure determined by the confine ment potential of the 2D HS. (C) 1998 Elsevier Science B.V. All rights reserved.