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arXiv · 2005.00304

Thickness dependence of electronic and crystal structures in VO$_2$ ultrathin films: suppression of the collaborative Mott-Peierls transition

D. Shiga·B. E. Yang·N. Hasegawa·T. Kanda·R. Tokunaga·K. Yoshimatsu·R. Yukawa·M. Kitamura·K. Horiba·H. Kumigashira
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Abstract

Through ${in~situ}$ photoemission spectroscopy, we investigated the change in the electronic and crystal structures of dimensionality-controlled VO$_2$ films coherently grown on TiO$_2$(001) substrates. In the nanostructured films, the balance between the instabilities of a bandlike Peierls transition and a Mott transition is controlled as a function of thickness. The characteristic spectral change associated with temperature-driven metal-insulator transition in VO$_2$ thick films holds down to 1.5 nm (roughly corresponding to five V atoms along the [001] direction), whereas VO$_2$ films of less than 1.0 nm exhibit insulating nature without V-V dimerization. These results suggest that the delicate balance between a Mott instability and a bandlike Peierls instability is modulated at a scale of a few nanometers by the dimensional crossover effects and confinement effects, which consequently induce the complicated electronic phase diagram of ultrathin VO$_2$ films.

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D. Shiga, B. E. Yang, N. Hasegawa, T. Kanda, R. Tokunaga, K. Yoshimatsu, R. Yukawa, M. Kitamura, K. Horiba, H. Kumigashira. 2020-05-01. Thickness dependence of electronic and crystal structures in VO$_2$ ultrathin films: suppression of the collaborative Mott-Peierls transition. https://doi.org/10.1103/physrevb.102.115114

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