Localised Wannier orbital basis for the Mott insulators GaV4S8 and GaTa4Se8

TL;DR

This study constructs localized Wannier orbital bases for GaV4S8 and GaTaSe8, enabling detailed analysis of their electronic and magnetic properties, and providing a foundation for future strong correlation studies.

Contribution

The paper develops accurate localized Wannier orbital bases for GVS and GTS, facilitating realistic modeling of their electronic structure and magnetic interactions.

Findings

Localized orbitals accurately reproduce bandstructures

Hopping amplitudes decrease rapidly with distance

Coulomb and Hund's interactions explain different ground states

Abstract

We study the electronic properties of GaV4S8 (GVS) and GaTaSe8 (GTS), two distant members within the large family of chalcogenides AM4X8, with A={Ga, Ge}, M={V, Nb, Ta, Mo} and X={S, Se}. While all these compounds are Mott insulators, their ground state show many types of magnetic order, with GVS being ferromagnetic and GTS non-magnetic. Based on their bandstructures, calculated with Density Functional Theory methods, we compute an effective tight binding Hamiltonian in a localised Wannier basis set, for each one of the two compounds. The localised orbitals provide a very accurate representation of the bandstructure, with hopping amplitudes that rapidly decrease with distance. We estimate the super-exchange interactions and show that the Coulomb repulsion with the Hund's coupling may account the for the different ground states observed in GVS and GTS. Our localised Wannier basis provides a starting point for realistic Dynamical Mean Field Theory studies of strong correlation effects in this family compounds.