Dressed j_eff-1/2 objects in mixed-valence lacunar spinel molybdates.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Chemistry

Background:

• Lacunar-spinel chalcogenides feature transition-metal tetrahedra with magnetic centers.
• Previous density-functional theory (DFT) suggested a single-configuration electronic ground state (a1^2 e^4 t2^5) for Mo4(13+) tetrahedra.

Purpose of the Study:

• To investigate the many-body electronic wave-function of the Mo4(13+) tetrahedron.
• To determine the influence of electron correlations and spin-orbit coupling on the magnetic properties.
• To provide a theoretical basis for understanding phase transitions in these materials.

Main Methods:

• Advanced many-body calculations to determine the tetramer wave-function.
• Analysis of electron correlation effects on the electronic configuration.
• Investigation of spin-orbit coupling effects within the valence orbital manifold.

Main Results:

• Sizable electron correlations reduce the weight of the previously postulated single-configuration state to 62%.
• Spin-orbit coupling effects and calculated g-factors deviate from predictions based on nominal j_eff = 1/2 moments.
• The study identifies 'dressing' of the spin-orbit j_eff = 1/2 object by intra-tetramer excitations.

Conclusions:

• The electronic ground state is more complex than a single configuration due to significant electron correlations.
• Observed deviations in magnetic properties are explained by the interplay of correlations and spin-orbit coupling.
• These findings offer a crucial theoretical foundation for understanding the exotic low-temperature phenomena in lacunar-spinel chalcogenides.