Electronic structure of TiSe${}_2$ from a quasi-self-consistent G${}_0$W${}_0$ approach

Abstract

In a previous work it was shown that the inclusion of exact exchange is essential for a first principles description of both the electronic- and the vibrational properties of TiSe${}_2$, M. Hellgren et al. [Phys. Rev. Lett. 119, 176401 (2017)]. The $GW$ approximation provides a parameter-free description of screened exchange but is usually employed perturbatively ($G_0{W}_0$) making results more or less dependent on the starting point. In this work, we develop a quasi-self-consistent extension of $G_0{W}_0$ based on the random phase approximation (RPA) and the optimized effective potential of hybrid density functional theory. This approach generates an optimal $G_0{W}_0$ starting-point and a hybrid exchange parameter consistent with the RPA. While self-consistency plays a minor role for systems such as Ar, BN and ScN, it is shown to be crucial for TiS${}_2$ and TiSe${}_2$. We find the high-temperature phase of TiSe${}_2$ to be a semi-metal with a band structure in good agreement with experiment. Furthermore, the optimized hybrid functional agrees well with our previous estimate and therefore accurately reproduces the low-temperature charge density wave phase.

arXiv comment11 pages, 5 figures

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• Trigonal-to-monoclinic structural transition in TiSe${}_2$ due to a combined condensation of $\text{q}=(\frac{1}{2},0,0)$ and $(\frac{1}{2},0,\frac{1}{2})$ phonon instabilities
• High-pressure II-III phase transition in solid hydrogen: Insights from state-of-the-art ab initio calculations
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• Self-consistent $GW$+Extended Dynamical Mean Field Theory for semiconductors and insulators
• Excitons and Optical Response in Excitonic Insulator Candidate TiSe${}_2$
• Intercalation induced quasi-freestanding layer in TiSe${}_2$