Decoupling structural and electronic dimensionality: 2D transport in a 3D honeycomb chiral stacking

Electronic dimensionality is ordinarily controlled by restricting orbital overlap through structure, exemplified by the weak interlayer bonding in van der Waals materials. HfSn 2 has strongly three-dimensional orbital overlap expressed in its bonding but displays robust 2D transport from open orbits at the Fermi surface. These states originate in the honeycomb layers that are present in HfSn 2 but hidden by the three-dimensional bonding. Chiral stacking of the honeycomb protects its electronic states in the presence of the strong interlayer orbital overlap. These states dominate macroscopic transport because the inversion symmetry breaking imposed by the stacking enhances mobility by locating Type II Weyl points on the 2D Fermi surface. Structural and electronic dimensionality can be decoupled by control of the arrangement of extended low-dimensional motifs to retain their electronic structures and augment functionality through the symmetry of the resulting scaffolds. This expands the design space for low-dimensional electronic materials beyond layered systems.