  Helices of increased electron density can spontaneously form in materials
containing multiple, interacting density waves. Although a macroscopic order
parameter theory describing this behaviour has been proposed and experimentally
tested, a detailed microscopic understanding of spiral electronic order in any
particular material is still lacking. Here, we present the elemental chalcogens
Selenium and Tellurium as model materials for the development of chiral charge
and orbital order. We formulate minimal models capturing the formation of
spiral structures both in terms of a macroscopic Landau theory and a
microscopic Hamiltonian. Both reproduce the known chiral crystal structure and
are consistent with its observed thermal evolution and behaviour under applied
pressure. The combination of microscopic and macroscopic frameworks allows us
to distil the essential ingredients in the emergence of helical charge order,
and may serve as a guide to understanding spontaneous chirality both in other
specific materials and throughout materials classes.
