The Letter explores the parametric excitation of low-frequency zonal flow induced by the beating of collisionless trapped ion and trapped electrons modes (CTIMs and CTEMs) and its feedback on the formation of transport barrier (TB). The zonal flow generation and the associated intermittent transport are investigated using a semi-Lagrangian gyrokinetic Vlasov simulations based on a Hamiltonian reduction technique, where both the fastest scales (cyclotron and bounce motions) are gyro-averaged. The model confirms the possibility to trigger TB by means of polarization effects, recently observed in global gyrokinetic simulations by A. Strugarek et al, Phys. Rev. Lett. 111 (2013) 145001.