Multiplicity of multi-bump type nodal solutions for a class of elliptic problems with exponential critical growth in ${\mathbb{R}}^2$

In this paper, we establish the existence and multiplicity of multi-bump nodal solutions for the following class of problems $$-\mathrm{\Delta }u+(\lambda V(x)+1)u=f(u),in{\mathbb{R}}^2,$$ where $\lambda \in (0,\mathrm{\infty })$, $f$ is a continuous function with exponential critical growth and $V:{\mathbb{R}}^2\to \mathbb{R}$ is a continuous function verifying some hypotheses.