Z₂ gauge field and topological chirality from Umklapp scattering in twisted graphite

Spinless systems exhibit unique topological characteristics compared to spinful ones, stemming from their distinct algebra. Without chiral interactions typically linked to spin, an intriguing yet unexplored interplay between topological and structural chirality may be anticipated. Here we show examples of spinless topological chirality solely from structural chirality in two types of twisted graphite. In a 3D helical structure, we find a chiral Weyl semimetal phase where bulk topology and chiral surface states are both determined by the screw direction. And in a 3D periodic structure formed with alternating twisting angle signs, a higher-order Dirac semimetal with chiral hinge states is discovered. Underlying these novel topological states is the Umklapp scattering that captures the chirality of the twisted interfaces, leading effectively to a sign-flipped chiral interlayer hopping, thereby introducing Z₂ lattice gauge field that alters the symmetry algebra. Our findings point to a new pathway for engineering topological chirality.