Elastic Response and Instabilities of Anomalous Hall Crystals

Abstract: Anomalous Hall crystals (AHCs) are exotic phases of matter that simultaneously break continuous translation symmetry and exhibit the quantum anomalous Hall effect. AHCs have recently been proposed as an explanation for the observation of an integer quantum anomalous Hall phase in a multilayer graphene system. Despite intense theoretical and experimental interest, little is known about the mechanical properties of AHCs. We study the elastic properties of AHCs, first by utilizing a continuum model with uniform Berry curvature. In contrast to Wigner crystals, we find that the stiffness of the AHC weakens and eventually vanishes as electronic interactions are increased. Furthermore, we demonstrate that the triangular lattice AHC arising in an experimentally relevant parameter regime of a realistic model of rhombohedral pentalayer graphene is unstable, emphasizing the importance of understanding the mechanical properties of AHCs for interpreting experiments.