$\alpha =\beta =\mu =1$ $\begin{array}{l}{U}_{1,2}=±\sqrt{\frac{-1+i\sqrt{3}}{2}}\\ {U}_{3,4}=±\sqrt{\frac{-1-i\sqrt{3}}{2}}\end{array}$ −1 −1 1 −1 Spirals Spirals Spirals Asymptotically stable Unstable Unstable $\alpha =1,\beta =\mu =-1$ $\begin{array}{l}{U}_{1,2}=±\sqrt{\frac{-1-i\sqrt{5}}{2}}\\ {U}_{3,4}=±\sqrt{\frac{-1+i\sqrt{5}}{2}}\end{array}$ −1 −1 1 −1 Saddles Saddles Saddles Saddles Unstable Unstable Unstable Unstable $\alpha =1,\beta =-1,\mu =0.01$ $\begin{array}{l}{U}_{1,2}=±\sqrt{\frac{-1+\sqrt{0.96}}{0.02}}\\ {U}_{3,4}=±\sqrt{\frac{1-\sqrt{0.96}}{0.02}}\end{array}$ −1 −1 1 −1 Spirals Spirals Saddle Asymptotically stable Unstable Unstable Unstable Unstable $\alpha =-1,\beta =\mu =1$ $\begin{array}{l}{U}_{1,2}=±\sqrt{\frac{-1+\sqrt{5}}{2}}\\ {U}_{3,4}=±\sqrt{\frac{-1-\sqrt{5}}{2}}\end{array}$ −1 −1 1 −1 Spirals Spirals Spirals Spirals Asymptotically stable Unstable Asymptotically stable Unstable $\alpha =-1,\beta =1,\mu =-0.02$ ${U}_{1,2}=±\sqrt{\frac{1-\sqrt{0.92}}{0.04}}$ −1 −1 1 −1 Spirals Saddles Saddles Saddles Asymptotically stable Unstable Unstable Unstable