Multi-bump solutions for Choquard equation with deepening potential well

We study the existence of multi-bump solutions to Choquard equation $$\begin{array}{l}-\mathrm{\Delta }u+(\lambda a(x)+1)u={\displaystyle (\frac{1}{\mathrm{\mid }x{\mathrm{\mid }}^{\mu }}\ast \mathrm{\mid }u{\mathrm{\mid }}^p)\mathrm{\mid }u{\mathrm{\mid }}^{p-2}uin{\mathbb{R}}^3,}\end{array}$$ where $\mu \in (0,3),p\in (2,6-\mu )$, $\lambda$ is a positive parameter and the nonnegative function $a(x)$ has a potential well $\mathrm{\Omega }:=int(a^{-1}(0))$ consisting of $k$ disjoint bounded components $\mathrm{\Omega }:={\cup }_{j=1}^k{\mathrm{\Omega }}_j$. We prove that if the parameter $\lambda$ is large enough then the equation has at least $2^k-1$ multi-bump solutions.