Electronic structure of the incommensurate metal Hg _{3- δ}asF₆

The electronic structure of Hg_{3- delta}AsF₆ has been considered in a model which takes the incommensurability of the Hg linear chains with the AsF₆ anion lattice into account. Despite the strength of the potential, the authors find that symmetry properties and selection rules play a dominant role in causing some matrix elements connecting states on the Fermi surface to vanish, in analogy with the conservation of crystal momentum in commensurate systems. By considering the effects of incommensurability, very good agreement is found with experimental de Haas-van Alphen data. They find that, paradoxically, some orbits in these materials exist in the absence of long-range order only.