Many-body effects in TiSe2: Can GW describe an Excitonic Insulator?
Abstract
We present both theoretical ab initio GW and experimental angle-resolved photoemission (ARPES) and scanning tunneling (STS) spectroscopy results on TiSe2. With respect to the density-functional Kohn-Sham metallic picture, the many-body GW self-energy leads to a ~ 0.2 eV band gap insulator consistent with our STS spectra at 5 K. The band shape is strongly renormalized, with the top-of-valence moved towards a circle of points away from , arising in a mexican hat feature typical of an excitonic insulator. Our calculations are in good agreement with experiment.
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