  For H-mode, standard decorrelation theory predicts that it is the turbulence
intensity $|\phi_k|^2$ that is mainly affected via flow-induced shearing of
turbulent eddies. However, for other regimes (e.g. I-mode, characterized by
high energy confinement but low particle confinement), this decrease of
turbulence amplitude cannot explain the decoupling of particle v.s. thermal
flux, since a suppression of turbulence intensity $|\phi_k|^2$ would
necessarily affect both fluxes the same way. Here, we explore a possible new
stabilizing mechanism: zonal flows may directly affect the transport
crossphase. We show the effect of this novel mechanism on the turbulent
particle flux, by using a simple fluid model [Baver et al., Phys. Plasmas
\textbf{9}, 3318 (2002)] for dissipative trapped-electron mode (DTEM),
including zonal flows. We first derive the evolution equation for the transport
crossphase $\delta_k$ between density and potential fluctuations, including
contributions from the $E \times B$ nonlinearity. By using a parametric
interaction analysis, we obtain a predator-prey like system of equations for
the pump amplitude $\phi_p$, the pump crossphase $\delta_p$, the zonal
amplitude $\phi_z$ and the triad phase-mismatch $\Delta \delta$. The system
displays limit-cycle oscillations where the instantaneous DTEM growth rate -
proportional to the crossphase - shows quasi-periodic relaxations where it
departs from that predicted by linear theory.
