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Chiral Charge Density Waves in Transition Metal Dichalcogenide

Ettore Carpene*

  • *Contact author: ettore.carpene@cnr.it
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Phys. Rev. Lett. 137, 066902 – Published 6 August, 2026

DOI: https://doi.org/10.1103/5vkg-zvhv

Abstract

The emergence of chirality in the charge density wave (CDW) phase of 1T−TiSe2 has recently attracted significant attention, yet its microscopic origin remains debated. The prevailing interpretation attributes chirality to a relative phase shift between the charge density components. Here, using density functional theory and symmetry analysis, it is demonstrated that such phase-shifted states entail prohibitive energy costs, rendering them unlikely candidates for the ground state. Instead, a nearly degenerate metastable CDW phase stacking order with monoclinic symmetry is identified that naturally breaks mirror and inversion symmetries. The CDW in 1T−TiSe2 possesses a dual physical nature: The electronic charge redistribution is intrinsically bond modulated, while the periodic lattice distortion is atom-centered transverse. This spatial separation allows a specific optical coupling mechanism where circularly polarized light breaks the energetic degeneracy between chiral domains. These results reconcile conflicting experimental observations, identifying the “spontaneous” chirality observed in local probes as a statistical distribution of CDW phase stacking domains while establishing the mechanism for macroscopic, light-induced gyrotropic order.

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Phys. Rev. Lett. 137, 066902– Published 6 August, 2026
  • Received 4 February 2026
  • Revised 28 April 2026
  • Accepted 10 July 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

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