Apparent Inconsistency of Observed Composite Fermion Geometric Resonances and Measured Effective Mass

Abstract
New ultrahigh frequency surface acoustic waves (SAW) on a high density 2D electron system demonstrate large principle and secondary geometric resonances of the cyclotron orbits of composite fermions (CF) with the acoustic waves. The effective mass as derived from dc transport produces a CF cyclotron frequency near the resonance structures comparable to the SAW frequency. A simplistic model of noninteracting CF's in semiclassical motion with such a cyclotron frequency is inconsistent with observation of the resonances.