Ground state solutions for non-autonomous fractional Choquard equations

We consider the following nonlinear fractional Choquard equation, \begin{equation}\label{e:introduction} \begin{cases} (-\Delta)^{s} u + u = (1 + a(x))(I_\alpha \ast (|u|^{p}))|u|^{p - 2}u\quad\text{ in }\mathbb{R}^N,\\ u(x)\to 0\quad\text{ as }|x|\to \infty, \end{cases} \end{equation} here $s\in (0, 1)$, $\alpha\in (0, N)$, $p\in [2, \infty)$ and $\frac{N - 2s}{N + \alpha} < \frac{1}{p} < \frac{N}{N + \alpha}$. Assume $\lim_{|x|\to\infty}a(x) = 0$ and satisfying suitable assumptions but not requiring any symmetry property on $a(x)$, we prove the existence of ground state solutions.