Moyen amphi (LPS
Bât 510, Orsay (91)


08 Nov 2021



Michele CASULA, Manipulating Dirac states by varying the strength of electron correlations in BaNi(Co)S_2

Michele Casula, UPMC

After having been considered as a potential candidate for high-temperature superconductivity, the BaNi(Co)S_2 compound has seen renewed attention for its topological properties. BaNiS_2 is a Dirac semimetal, with 4 Dirac cones lying at the Fermi level, protected by the non-symmorphic symmetry and generated by an inversion mechanism triggered by a strong p-d hybridization.  We show that these cones can be effectively tuned by doping the compound through Co/Ni substitution [1], or by photo-exciting it [2]. By theoretical analysis and numerical modelization, we explain how chemical substitution and photo-excitation change its correlation strength. BaNi_xCo_{1-x}S_2 Dirac semimetal undergoes a transition at x=0.2 towards a strongly correlated insulating phase, while the non-equilibrium modifications of the Dirac bands are triggered by nontrivial band shifts mainly induced by the Fock term and by a change of the screening properties in the system [3]. The mechanisms unveiled in BaNi(Co)S_2 could guide the search of other tunable Dirac materials.

[1] Niloufar Nilforoushan, Michele Casula, Adriano Amaricci, Marco Caputo, Jonathan Caillaux, Lama Khalil, Evangelos Papalazarou, Pascal Simon, Luca Perfetti, Ivana Vobornik, Pranab Kumar Das, Jun Fujii, Alexei Barinov, David Santos-Cottin, Yannick Klein, Michele Fabrizio, Andrea Gauzzi, and Marino Marsi, PNAS 118, 33 (2021).[2] N. Nilforoushan, M. Casula, M. Caputo, E. Papalazarou, J. Caillaux, Z. Chen, L. Perfetti,  A. Amaricci, D. Santos-Cottin, Y. Klein, A. Gauzzi, and M. Marsi, Photoinduced renormalization and electronic screening of quasi-two-dimensional Dirac states in BaNiS2, Phys. Rev. Research 2, 043397 (2020).[3] Nikolaj Bittner, Denis Golež, Michele Casula, and Philipp Werner, Photoinduced Dirac-cone flattening in BaNiS2, Phys. Rev. B 104, 115138 (2021).