Correlations in lacunar spinels: dynamical mean-field study with configuration interaction based impurity solver*

Density functional plus dynamical mean field methods are used to study the role of correlations in in lacunar spinel compounds GaM$_4$X$_8$ (M=Nb, Mo, Ta and and X=S, Se and Te) to investigate the interplay of correlations and topology in materials with strong spin-orbit coupling. A novel configuration-interaction exact diagonalization solver enables inclusion of more bath orbitals, enabling a better treatment of spectral functions and more accurate computations of phase boundaries. Focussing on GaTa$_4$Se$_8$, we discuss how the correlation induces metal-insulator transition in presence of the spin-orbit coupling, based on spectral functions and optical conductivities.