Faculté des sciences et de médecine

Linear behavior of the optical conductivity and incoherent charge transport in ${\mathrm{BaCoS}}_{2}$

Santos-Cottin, D. ; Klein, Y. ; Werner, Philipp ; Miyake, Takashi ; Medici, L. de ; Gauzzi, A. ; Lobo, R. P. S. M. ; Casula, Michele

In: Physical Review Materials, 2018, vol. 2, no. 10, p. 105001

Optical conductivity measurements on a BaCoS2 single crystal unveil an unusual linear behavior over a broad spectral range. In the paramagnetic phase above 300 K, the spectrum shows no gap, which contradicts the previously proposed scenario of a charge-transfer Mott insulator. Ab initio dynamical mean field theory calculations including a retarded Hubbard interaction explain the data in terms... More

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    Summary
    Optical conductivity measurements on a BaCoS2 single crystal unveil an unusual linear behavior over a broad spectral range. In the paramagnetic phase above 300 K, the spectrum shows no gap, which contradicts the previously proposed scenario of a charge-transfer Mott insulator. Ab initio dynamical mean field theory calculations including a retarded Hubbard interaction explain the data in terms of an incipient opening of a Co(3d)−S(3p) charge-transfer gap concomitant to incoherent charge transport driven by electronic correlations. These results point to a non-Fermi liquid scenario with Hund's metal properties in the paramagnetic state, which arises from an incipient Mott phase destabilized by low-energy charge fluctuations across the vanishing 3d−3p charge-transfer gap.