Exploring Dark Energy via Non-Minimal Coupling in $f(Q,L_m)$ Gravity with Gong-Zhang Parameterization

Abstract: In this study, we investigate the late-time accelerated expansion of the universe within the framework of non-minimally coupled $f(Q,L_m)$ gravity, where $Q$ is the non-metricity scalar and $L_m$ is the matter Lagrangian. We derive modified Friedmann equations in a flat FLRW background and employ the \textit{Gong-Zhang} parameterization for the DE equation of state (EoS), allowing an analytical form of the Hubble parameter $H(z)$. The model parameters are constrained using recent Cosmic Chronometers (CC) and Pantheon+SH0ES Type Ia supernova datasets through MCMC-based chi-squared minimization. We analyze various cosmological quantities including the deceleration parameter, EoS, jerk, snap, lerk, and diagnostic tools such as $Om(z)$ and the statefinder pair $(r,s)$. Our findings indicate a viable transition from deceleration to acceleration and reveal a quintessence-to-phantom-like evolution of dark energy. Furthermore, energy conditions are examined, showing a violation of the strong energy condition, consistent with current cosmic acceleration. The results establish that the $f(Q,L_m)$ framework with non-minimal coupling and parameterized EoS provides a compelling alternative to $\Lambda$CDM in describing cosmic acceleration.