Electron correlations rule the phonon-driven instability in single-layer TiSe2

We investigate the controversial case of the charge-density-wave (CDW) order in single-layer 1T-TiSe2 by employing the density functional perturbation theory with on-site Hubbard interactions. The results emphasize the crucial role of electron correlations via Hubbard corrections in order to capture the accurate electronic structure, low- and high-temperature limits of the CDW phonon mode, and temperature-charge phase diagram. We show, in close agreement with the experiments, that the total phase diagram consists of both commensurate and incommensurate CDW regions, where the latter coincides with the superconductive phase and might be instrumental for its formation. In addition to the established roles of quantum lattice fluctuations and excitonic interactions, our analysis emphasizes the overlooked crucial role of the momentum-dependent electron-phonon coupling and electron correlations for the CDW phase transition in single-layer TiSe2.

Automated summary

We investigate the controversial case of charge-density-wave (CDW) order in single-layer 1T-TiSe2 using density functional perturbation theory with on-site Hubbard interactions. Our results highlight the crucial role of electron correlations via Hubbard corrections in accurately capturing the electronic structure, low- and high-temperature limits of the CDW phonon mode, and the temperature-charge phase diagram. In agreement with experiments, we show that the total phase diagram of 1T-TiSe2 consists of both commensurate and incommensurate CDW regions, where the latter coincides with the superconducting phase and may play a significant role in its formation. Additionally, our analysis emphasizes the overlooked importance of momentum-dependent electron-phonon coupling and electron correlations for the CDW phase transition in single-layer TiSe2.