Schedule Nov 03, 2009
Recent Theoretical Development for Local Excitations in Correlated Charge-Transfer Insulators
Wei Ku (BNL)

Recent theoretical developments to better understand strongly bound local Frenkel excitons in “charge-transfer insulators” will be presented. First, the description of charge-transfer insulators will be unified with that of the Mott insulators via the use of symmetry-respecting first-principles Wannier functions. Second, formal theoretical framework of TD-DFT with LDA+U will be developed and applied to a case study illustrating its capability and deficiency. Third, systematic framework of strong coupling approach will be presented to account for the multiplets beyond the typical first-principles approximations. Finally, a two-particle hopping kernel is introduced to describe propagation of the local excitations. Case studies include anisotropy of local excitations in NiO [1], missing neutron spectral weight of the cuprates [2], and space-time propagation of excitons in LiF [3].

[1] B. Larson et al, Phys. Rev. Lett 99, 026401 (2007).
[2] I. Zaliznyak et al, to appear in Nature Physics (2009).
[3] P. Abbamonte et al, Proc. Natl. Acad. Sci. 105, 12159 (2008).

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