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Ricardo Lobo

ESPCI Paris – PSL University – CNRS – Sorbonne Université, France

Correlations and dispersive Dirac physics in the quantum material family BaCoS2-BaNiS2 – Reverse band-structure engineering of the optical conductivity

When: 12:00-13:00 CET, May 30th (Thursday), 2024

Where: Seminar Room (182), ICMM-CSIC, Campus de Cantoblanco, Madrid

BaCoS2 and BaNiS2 are the end members of a solid solution that shows a vast array of quantum properties. The Co material is close to a strongly correlated insulator with an antiferromagnetic transition, as well as a structural phase transition, around room temperature. At 28% Ni doping this material undergoes an electronic metal-insulator phase transition to a Drude metal. The metallic state persists all the way to the pure Ni compound. At this point, in addition to a Drude peak, we observe a strong contribution from bands with linear dispersion at the Fermi level, which give origin to dispersive Dirac nodal lines. We measured the optical conductivity of these materials and combined them with ab-initio calculations to reverse engineer the role of each band in the physical response of these materials. We explained uncommon features in their optical response such as a linear dispersion of the optical conductivity [1] and the existence of an isosbestic line separating a spectral-weight transfer across Dirac nodal states [2].

[1] D. Santos-Cottin, Y. Klein, P. Werner, T. Miyake, L. de’Medici, A. Gauzzi, R.P.S.M. Lobo, and M. Casula, Linear behavior of the optical conductivity and incoherent charge transport in BaCoS2, Phys. Rev. Materials 2, 105001 (2018). arXiv: 1712.01539.

[2] D. Santos-Cottin, M. Casula, L. de’Medici, F. Le Mardelé, J. Wyzula, M. Orlita, Y. Klein, A. Gauzzi, A. Akrap, and R.P.S.M. Lobo, Optical conductivity signatures of open Dirac nodal lines, Phys. Rev. B 104, L201115 (2021). arXiv: 2104.05521.