On ground states for the Schrödinger-Poisson system with periodic potentials

This paper is concerned with the following Schrodinger-Poisson system $$\left\{ {\begin{array}{*{20}{c}} { - \Delta u + V\left( x \right)u - K\left( x \right)\phi \left( x \right)u = q\left( x \right){{\left| u \right|}^{p - 2}}u,}&{in\;{\mathbb{R}^3},} \\ { - \Delta \phi = K\left( x \right){u^2},}&{in\;{\mathbb{R}^3},} \end{array}} \right.$$ where p ∈ (2, 6), V(x) ∈ C(ℝ3, ℝ) is a general periodic function, K(x) and q(x) are nonperiodic functions. Under suitable assumptions, we prove the existence of ground state solutions via variational methods for strongly indefinite problems.