A comprehensive dynamical and phenomenological analysis of structure growth in curvature-modulated coupled quintessence scenario

Abstract: We investigate an interacting dark energy-dark matter model within the quintessence framework, characterized by the coupling term $Q_0 = \alpha \kappa \rho_m \dot{\phi} \left[1 - \beta R^2/(6H^2) \right]$, and the scalar field evolves under an exponential potential $V(\phi) = V_0 e^{-\lambda \kappa \phi}$, with parameters $\alpha$, $\lambda$, and $\beta$. Recasting the cosmological equations into a first-order autonomous system using dimensionless variables, we perform a phase space analysis to identify conditions for stable, non-phantom accelerating attractors. The Ricci scalar term, controlled by $\beta$, significantly affects the stability of critical points, with attractors transitioning to repellers for higher values of $\beta$. We also analyze linear scalar perturbations, focusing on the matter density contrast $\delta_m$ and the growth index $\gamma$. Additionally, we compute the deceleration and jerk parameters, the Hubble rate, and the distance modulus $\mu(z)$, showing good agreement with observational data. The model naturally addresses the cosmic coincidence problem through scalar field tracking behavior. For moderate parameter values, matter perturbations continue to grow into the future, capturing both background and perturbative dynamics effectively. This framework thus offers a consistent and observationally viable approach to interacting dark energy.