Dresden 2009 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 9: Correlated Electrons: Metal-Insulator Transition 1

TT 9.7: Vortrag

Montag, 23. März 2009, 15:45–16:00, HSZ 03

Is NiS₂ a charge-transfer insulator? — •Jan Kuneš¹, Dmitry A Korotin², and Vladimir I Anisimov² — ¹Theoretical Physics III, Center for Electronic Correlations and Magnetism, University of Augsburg, Augsburg, Germany — ²Institute of Metal Physics, Russian Academy of Sciences, Yekaterinburg, Russia

The physics NiS₂ and NiSe₂ is often described in terms of small respectively negative gap charge-transfer insulator. Using combination of first principles bandstructure and dynamical mean-field approximation, so called LDA+DMFT approach, we investigate the electronic structures of the two materials at ambient conditions and under pressure. While both compounds are similar to charge-transfer insulators in that the ligand p-band is located between the Ni-d lower and upper Hubbard bands, the quasiparticle gap is not of the charge-transfer type. The gap is between a strongly hybridized p−d valence band and a conduction band formed by anti-bonding states of S-S dimer with strong admixture of Ni-d character. The key difference between NiS₂ and NiSe₂ determining their groundstates is the stronger dimer splitting in the former.