It i well-known that the Laplace operator generate an analytic semigroup for example in $L^2(\Omega)$ on nice domains $\Omega \in \mathbb{R}^n$.
Now does also the Bi-Laplacian generate an analytic semigroup or at least a strongly continuous one? Can you provide references?
Yes, the bi-Laplacian with Dirichlet boundary conditions generates an analytic semigroup on $L^p(\Omega), \; p\in (1,\infty)$. For $p=2$, you can show that the operator is self-adjoint. A general result was proved in Theorem 5.6, pp. 189 in