Zenker, B. Fehske, H. Beck, Hans Monney, Claude Bishop, A. R. 2013-08-23 We address the question of the origin of the recently discovered chiral property of the charge-density-wave phase in 1<i>T</i>-TiSe₂, which so far lacks a microscopic understanding. We argue that the lattice degrees of freedom seem to be crucial for this novel phenomenon. We motivate a theoretical model that takes into account one valence and three conduction bands, a strongly screened Coulomb interaction between the electrons, as well as the coupling of the electrons to a transverse optical phonon mode. The Falicov-Kimball model extended in this way possesses a charge-density-wave state at low temperatures, which is accompanied by a periodic lattice distortion. The charge ordering is driven by a lattice deformation and electron-hole pairing (excitonic) instability in combination. We show that both electron-phonon interaction and phonon-phonon interaction must be taken into account at least up to quartic order in the lattice displacement to achieve a stable chiral charge order. The chiral property is exhibited in the ionic displacements. Furthermore, we provide the ground-state phase diagram of the model and give an estimate of the electron-electron and electron-phonon interaction constants for 1<i>T</i>-TiSe₂. application/pdf https://folia.unifr.ch/global/documents/303252 https://folia.unifr.ch/documents/303252/files/bec_cco.pdf eng info:eu-repo/semantics/altIdentifier/doi/10.1103/PhysRevB.88.075138 info:eu-repo/semantics/openAccess License undefined Physical Review B. - 2013, vol. 88, no. 7, p. 075138 info:eu-repo/classification/udc/53 Chiral charge order in 1<i>T</i>-TiSe₂: Importance of lattice degrees of freedom http://purl.org/coar/resource_type/c_6501