Abstract :
We propose a theory for the new maximum recently observed by Willett et al. [Phys. Rev. Lett., 83 (1999) 2624] in the longitudinal magnetoresistance of a weakly modulated two-dimensional electron gas (2DEG) near filling factor ν=1/2 for the current driven along the modulation lines. The maximum is superimposed upon a new resonance structure. This occurs due to the geometric resonance of composite fermion cyclotron orbits with the period of modulation of the effective magnetic field. We propose here a semiquantitative theory of the dc magnetotransport in a modulated 2DEG near one half filling. Our analysis is based on the Boltzmann transport equation and it enables us to obtain this maximum which was neither observed nor predicted previously.
