Quasiparticle band structure of vanadium dioxide.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Computational Quantum Chemistry

Background:

• Vanadium dioxide (VO2) exhibits a metal-insulator transition near room temperature.
• Experimental observations show VO2 is insulating below 340 K.
• Standard electronic structure calculations, like Local Density Approximation (LDA), predict a gapless state for VO2.

Purpose of the Study:

• To resolve the discrepancy between experimental and calculated electronic properties of VO2.
• To investigate the role of many-body self-energy effects in VO2.
• To accurately determine the quasiparticle band structure of VO2.

Main Methods:

• Ab initio GW (Green's function) method was employed.
• Calculations focused on self-energy effects and dynamical correlations.
• Kohn-Sham basis set was utilized, considering off-diagonal matrix elements.

Main Results:

• The self-energy in VO2 is strongly energy-dependent.
• Dynamical effects are crucial for accurate quasiparticle energy calculations.
• Including off-diagonal matrix elements in the Kohn-Sham basis is important for band disentanglement.
• The combined effects open a direct band gap in VO2, consistent with experimental findings.

Conclusions:

• The insulating nature of VO2 below 340 K is explained by including many-body self-energy and dynamical effects.
• Simple LDA calculations are insufficient to capture the insulating behavior.
• Self-consistent GW calculations are essential for accurate predictions of VO2 electronic properties.