Detection of composite fermions by magnetic focusing

Abstract

We report on transverse magnetic focusing experiments in two-dimensional electron systems in the vicinity of Landau level filling factor \ensuremath{\nu}=1/2. We observe quasiperiodic magnetic focusing peaks for \ensuremath{\nu}1/2 and no periodic structure for \ensuremath{\nu}>1/2 in several double-constriction GaAs heterojunction samples. The quasiperiod and the direction of focusing in all of these samples are in good quantitative agreement with that expected from semiclassical transport by composite fermions of charge -\ensuremath{\Vert}e\ensuremath{\Vert}.