Electronic phase separation and emergence of a nondimerized insulating phase in VO$_2$ $(110)_{\mathit{R}}$ ultrathin films
Year: 2026
Type: preprint
Abstract: Using in situ photoemission spectroscopy and x-ray absorption spectroscopy, we investigated the thickness dependence of the electronic structure and V-V dimerization in VO$_2$/TiO$_2$ (110) ultrathin films, in which the one-dimensional V-V chains along the $c_{\mathit{R}}$ axis lie in the film plane. In VO$_2$ $(110)_{\mathit{R}}$ films, the reduction in dimensionality along the surface-normal direction is not expected to impose a geometric constraint on V-V dimerization, unlike in VO$_2$ $(001)_{\mathit{R}}$ films. Nevertheless, the characteristic spectral changes associated with the temperature-driven metal-insulator transition observed in thick films persist down to 1.5 nm, whereas at 1 nm an insulating electronic phase is observed without V-V dimerization. This behavior is highly similar to that reported for VO$_2$ $(001)_{\mathit{R}}$, suggesting that the enhancement of Mott instability resulting from reduced dimensionality is a common and essential driving force for the emergence of the nondimerized insulating phase in VO$_2$ ultrathin films. Meanwhile, unlike in VO$_2$ $(001)_{\mathit{R}}$, the nondimerized insulating phase in VO$_2$ $(110)_{\mathit{R}}$ coexists with the phase exhibiting the temperature-driven metal-insulator transition. Its fraction increases exponentially with decreasing thickness and becomes dominant at 1 nm. The corresponding effective critical thickness is estimated to be 2.2 nm. These results imply that the geometric orientation of the V-V chains dictates the spatial evolution of electronic phase separation via strain-mediated phase competition.
Source: arXiv (Cornell University)
Language: English
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
Awards: Development of transparent Mott devices using operant ARPES, G2451401391, G3104958147, Development of resonant-tunneling Mott transistor based on double quantum well structures of strongly correlated oxides, Multidisciplinary analysis of oxide devices and interfaces using the international network of next generation synchrotron-radiation facilities, G4573196265, G5332192529, Renaissance of Transition Metal Oxides: New Superconductivity in Hetero d-Electron Oxide Systems, 強相関酸化物界面設計に基づく電子・結晶構造相転移の独立制御, Elucidation of Collective Electronic Phase Transition Induced at Device Interfaces Based on Correlated Oxides, G72856978, G8831298913, G898776848
OpenAlex ID: W7204917957