Phonon anharmonicity and electron-phonon coupling in pure and doped VO2

Important insights into the thermodynamics and mechanism of the VO2 MIT were achieved by probing lattice dynamics using IXS[1] and ultrafast pump-probe x-ray diffraction[2]. But detailed phonon dispersions for the insulating M1 phase have yet to be reported. In addition, abnormally low electronic thermal conductivity in Rutile VO2 requires further examination of phonon anharmonicity and electron-phonon coupling[3]. We report new measurements of phonon dispersions in VO2 and doped crystals, as well as DFT simulations of phonon dispersions and spectral functions. Our results explain the origin of strong phonon damping in Rutile VO2, compared to M1 VO2 and Rutile TiO2, and assess the failure of perturbation theory in predicting accurate phonon linewidths. Our simulations capture the phonon damping behavior beyond perturbation theory, providing critical insights into the unusual lattice thermal conductivity.

1. Budai, J.D., et al., Nature, 2014. 515(7528): p. 535-539.
2. S. Wall*†, S. Yang,* et al., Science 362, pp. 572-576 (2018)
3. Lee, S., et al., Science, 2017. 355(6323): p. 371-374.