We present both theoretical ab-initio results within the Hedin's GW approximation and experimental angle-resolved photoemission and scanning tunneling spectroscopy measurements 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 highest valence and the lowest conduction bands are strongly renormalized, with a loss of k2 parabolic dispersion toward a k4 shape. In particular, GW moves the top of valence moved toward a circle of points away from Γ, arising in a Mexican hat shape commonly associated with an excitonic insulator. Our calculations are in good agreement with experiment.
Ab initio many-body effects in TiSe2 : a possible excitonic insulator scenario from GW band-shape renormalization / M. Cazzaniga, H. Cercellier, M. Holzmann, C. Monney, P. Aebi, G. Onida, V. Olevano. - In: PHYSICAL REVIEW. B, CONDENSED MATTER AND MATERIALS PHYSICS. - ISSN 1098-0121. - 85:19(2012), pp. 195111.195111.1-195111.195111.6. [10.1103/PhysRevB.85.195111]
Ab initio many-body effects in TiSe2 : a possible excitonic insulator scenario from GW band-shape renormalization
M. CazzanigaPrimo
;G. OnidaPenultimo
;
2012
Abstract
We present both theoretical ab-initio results within the Hedin's GW approximation and experimental angle-resolved photoemission and scanning tunneling spectroscopy measurements 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 highest valence and the lowest conduction bands are strongly renormalized, with a loss of k2 parabolic dispersion toward a k4 shape. In particular, GW moves the top of valence moved toward a circle of points away from Γ, arising in a Mexican hat shape commonly associated with an excitonic insulator. Our calculations are in good agreement with experiment.Pubblicazioni consigliate
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