Critical Role of the Exchange Interaction for the Electronic Structure and Charge-Density-Wave Formation in TiSe_{2}

• Published in: Physical review letters Vol. 119; no. 17; p. 176401
• Main Authors: Hellgren, Maria, Baima, Jacopo, Bianco, Raffaello, Calandra, Matteo, Mauri, Francesco, Wirtz, Ludger
• Format: Journal Article
• Language: English
• Published: United States 27.10.2017
• ISSN: 1079-7114
• DOI: 10.1103/PhysRevLett.119.176401

We show that the inclusion of screened exchange via hybrid functionals provides a unified description of the electronic and vibrational properties of TiSe_{2}. In contrast to local approximations in density functional theory, the explicit inclusion of exact, nonlocal exchange captures the effects of the electron-electron interaction needed to both separate the Ti-d states from the Se-p states and stabilize the charge-density-wave (CDW) (or low-T) phase through the formation of a p-d hybridized state. We further show that this leads to an enhanced electron-phonon coupling that can drive the transition even if a small gap opens in the high-T phase. Finally, we demonstrate that the hybrid functionals can generate a CDW phase where the electronic bands, the geometry, and the phonon frequencies are in agreement with experiments.