Is the subgroup of $GL(2,\mathbb Z)$ generated by the matrices $$ \begin{pmatrix} 1&1 \\ 1&0\end{pmatrix}\ \ \text{and} \ \ \begin{pmatrix} 2&1 \\ 1&0\end{pmatrix} $$ free?

I am sure this is well known, so any relevant references will be appreciated.

My motivation comes from dynamical systems where these matrices specify two automorphisms of the 2-torus; I am interested in studying the orbits of their joint action.