$N=2$ supersymmetric structures on classical $W$-algebras

We describe an $N=2$ supersymmetric Poisson vertex algebra structure of $N=1$ (resp. $N=0$) classical $W$-algebra associated with $\mathfrak{sl}(n+1|n)$ and the odd (resp. even) principal nilpotent element. This $N=2$ supersymmetric structure is connected to the principal $\mathfrak{sl}(2|1)$-embedding in $\mathfrak{sl}(n+1|n)$ superalgebras, which are the only basic Lie superalgebras that admit such a principal embedding.