Occupation switching of d orbitals in vanadium dioxide probed via hyperfine interactions

概要

Metal-insulator transition was microscopically investigated by orbital-resolved nuclear magnetic resonance (OR-NMR) spectroscopy in a single crystal of vanadium dioxide VO2. Observations of the anisotropic 51V Knight shift and the nuclear quadrupole frequency allow us to evaluate orbital-dependent spin susceptibility and d orbital occupations. The result is consistent with the degenerated t2g orbitals in a correlated metallic phase and the d orbital ordering in a nonmagnetic insulating phase. The predominant orbital pointing along the chain facilitates a spin-singlet formation triggering metal-insulator transition. The asymmetry of magnetic and electric hyperfine tensors suggests the d orbital reformation favored by a low-symmetry crystal field, forming a localized molecular orbital. The result highlights the cooperative electron correlation and electron-phonon coupling in Mott transition with orbital degrees of freedom.

この論文で使われている画像