# Why does my loop not show?

I have a big picture made, but I can't get my nodes to get a loop (an arrow to itself).

My code:

\begin{tikzpicture}
\matrix (mat) [matrix of nodes]
{
|[draw,circle]|$(0)$  &[10mm] $\begin{bmatrix} u^{(0)}_0 \\ u^{(0)}_1 \end{bmatrix}$ & $\begin{bmatrix} \sigma^{(0)}_{00} & \sigma^{(0)}_{01} \\ \sigma^{(0)}_{10} & \sigma^{(0)}_{11} \end{bmatrix}$ & \\
|[draw,circle]|$(1)$ & $\begin{bmatrix} u^{(1)}_0 \\ u^{(1)}_1 \end{bmatrix}$ & $\begin{bmatrix} \sigma^{(1)}_{00} & \sigma^{(1)}_{01} \\ \sigma^{(1)}_{10} & \sigma^{(1)}_{11} \end{bmatrix}$ &  $\begin{bmatrix} u^{(0)}_0 \\ u^{(0)}_1 \\ u^{(1)}_0 \\ u^{(1)}_1 \\ u^{(2)}_0 \\ u^{(2)}_1 \end{bmatrix}$ \\
|[draw,circle]|$(2)$ & $\begin{bmatrix} u^{(2)}_0 \\ u^{(2)}_1 \end{bmatrix}$ & $\begin{bmatrix} \sigma^{(2)}_{00} & \sigma^{(2)}_{01} \\ \sigma^{(2)}_{10} & \sigma^{(2)}_{11} \end{bmatrix}$ &   \\
};

\draw [->] (mat-1-1) -- (mat-2-1);
\draw [->] (mat-2-1) to [bend right=35] (mat-1-1);
\draw [->] (mat-2-1) -- (mat-3-1);
\draw [->] (mat-3-1) to [bend right=35] (mat-2-1);

\draw [->] (mat-1-1) to [bend left=55] (mat-3-1);
\draw [->] (mat-3-1) to [bend left=55] (mat-1-1);

\draw [->,loop above,looseness=16,min distance=15mm] (mat-1-1);

\end{tikzpicture}


The interesting part is the last \draw command which doesn't seem to have any effect. What should I do to display a loop above my node?

Currently it looks like this:

-
\draw (mat-1-1) to [->,loop above,looseness=16,min distance=15mm] (mat-1-1);