Ground States of Fermionic Nonlinear Schrödinger Systems with Coulomb Potential I: The $L^2$-Subcritical Case

We consider ground states of the $N$ coupled fermionic nonlinear Schrödinger systems with the Coulomb potential $V(x)$ in the $L^2$-subcritical case. By studying the associated constraint variational problem, we prove the existence of ground states for the system with any parameter $\alpha >0$, which represents the attractive strength of the non-relativistic quantum particles. The limiting behavior of ground states for the system is also analyzed as $\alpha \to \mathrm{\infty }$, where the mass concentrates at one of the singular points for the Coulomb potential $V(x)$.