Journal article

Chiral charge order in 1T-TiSe₂: Importance of lattice degrees of freedom

  • Zenker, B. Institut für Physik, Ernst-Moritz-Arndt-Universität Greifswald, Germany
  • Fehske, H. Institut für Physik, Ernst-Moritz-Arndt-Universität Greifswald, Germany
  • Beck, Hans Département de Physique and Fribourg Center for Nanomaterials, Université de Fribourg, Switzerland
  • Monney, Claude Fritz-Haber-Institut der Max Planck Gesellschaft, Berlin, Germany
  • Bishop, A. R. Theory, Simulation, and Computation Directorate, Los Alamos National Laboratory, New Mexico, USA
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  • Physical Review B. - 2013, vol. 88, no. 7, p. 075138
English We address the question of the origin of the recently discovered chiral property of the charge-density-wave phase in 1T-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 1T-TiSe₂.
Faculté des sciences et de médecine
Département de Physique
  • English
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