Analysis of diverging effective mass extracted from thermoelectric power across the metal-insulator transition in VO2

作者：Kang Manil; Kim Sok Won^*; Ryu Ji Wook

来源：Journal of Applied Physics, 2015, 118(3): 035105.

DOI：10.1063/1.4926860

In order to reveal the electron-electron correlation (interaction) effect in a Mott insulator VO2, we measured the temperature dependence of the thermopower, Hall effect, and Raman spectra in VO2 films and extracted the diverging effective mass from the thermoelectric behavior in the metal-insulator transition (MIT) region, using a combination of the thermopower formula for two-dimensional electron system and the extended Brinkman-Rice (EBR) model explaining the correlation effect. The temperature dependence of the measured diverging thermoelectric power is closely fitted by the band-filling (rho) dependent effective mass mm = 1/(1-rho(4)) given in the EBR model. The diverging behavior is the effect of measurement and analyzed as the percolation phenomenon increasing the metal region with increasing temperature. The true effective mass in the metal region is regarded as constant regardless of rho. The true correlation strength kappa(BR) in the BR model deduced by extrapolation near rho = 1 is evaluated as kappa(BR) > 0.92. The Raman spectra showed decoupling between the MIT and the structural phase transition associated with lattice distortion induced by the electron-phonon interaction. Thus, we conclude the MIT in VO2 as a first-order Mott MIT induced by strong correlation regardless of the electron-phonon interaction.

• 出版日期2015-7-21