The Rise of Twist-Optics

Two-dimensional materials stacked with a relative twist angle have been the focus point of tremendous interest in the condensed matter community. In the last four months, a theoretical prediction and four independent experimental works have demonstrated the tremendous impact these results can have on the nanophotonics community: the phonon polariton dispersion of twisted stacks of MoO 3 crystals can range from hyperbolic to elliptic, depending on the twist angle and thicknesses. In this Perspective, we provide a fast introduction to this exciting new topic and explain the importance of these findings.