The similarity of irreducible operators in factors

An operator $T$ in a separable factor $\mathcal{M}$ is said to be irreducible in $\mathcal{M}$ if the von Neumann subalgebra $W^{\ast }(T)$ generated by $T$ is an irreducible subfactor of $\mathcal{M}$, i.e., $W^{\ast }(T{)}^{\mathrm{\prime }}\cap \mathcal{M}=\mathbb{C}I$. We say that $T$ is a single generator of $\mathcal{M}$ if $W^{\ast }(T)=\mathcal{M}$. In this paper, we study generators of separable factors related to maximal abelian self-adjoint subalgebras. As an application, we obtain a complete characterization of normal operators in separable factors which are similar to irreducible operators.