Cosmology in energy-momentum squared symmetric teleparallel gravity

In this letter, we explore the $f(Q,T_{\mu\nu}T^{\mu \nu})$ gravity theory, building upon the foundations laid by the $f(Q)$ and $f(Q,T)$ gravity theories. Here, $Q$ represents non-metricity and $T_{\mu\nu}$ stands for the energy-momentum tensor. The proposed action encompasses an arbitrary function of both non-metricity $Q$ and the square of the energy-momentum tensor, specifically $T^2=T_{\mu\nu}T^{\mu \nu}$. We find the analytical solution for the barotropic fluid case $p=\omega \rho$ for the model $f(Q, T_{\mu \nu}T^{\mu \nu}) = Q + \eta(T_{\mu \nu}T^{\mu \nu})$. We constrain parameters of the solution $H(z)$ utilizing CC, BAO, and latest Pantheon+SH0ES samples with the help of Monte Carlo Markov Chain sampling technique along with Bayesian statistical analysis. Further, from the Om diagnostic test, we find that the assumed cosmological model favors the quintessence regime.