Fig. 1.

The phase diagram with respect to the normalized dimensionless parameters $\alpha /\left(1+\alpha \right)$ and $\beta /\left(1+\beta \right)$. In the collinear phase, the Néel vectors of the two layers are constant and either aligned or counteraligned. The characteristics of the twisted phases are most obvious when the potential term plays the dominant role: in the twisted-s phase, ${\varphi }_s=\pi$, while the sign of $\cos {\varphi }_a$ exhibits modulations resembling those of $\widehat{\mathrm{\Phi }}\left(\mathsf{x}\right)$ (see Fig. 2A). In the twisted-a phase, on the other hand, the signs of both $\cos {\varphi }_s$ and $\cos {\varphi }_a$ follow that of $\widehat{\mathrm{\Phi }}\left(\mathsf{x}\right)$. The twisted-s phase terminates at $\left(0.88,0.94\right)$ near the right top corner of the diagram. The dashed line shows $\beta =10\alpha$, while the dotted line corresponds to $\beta =0.1\alpha$. For $\beta =\alpha$, the corresponding line would be the diagonal one connecting the left bottom and right top corners.