High resolution Hall measurements across the VO2 metal-insulator transition reveal impact of spatial phase separation

TL;DR

High-resolution Hall measurements across the VO2 metal-insulator transition reveal that the transition is driven by spatial phase separation rather than mobility change, emphasizing the role of nanoscale domain coexistence in correlated oxides.

Contribution

This study provides the first high-resolution Hall measurement analysis showing that the MIT in VO2 is linked to phase separation, not mobility change, challenging prior assumptions.

Findings

MIT is not correlated with mobility change

Spatial phase separation accompanies the MIT

Nano-scale domains retain bulk properties

Abstract

Many strongly correlated transition metal oxides exhibit a metal-insulator transition (MIT), the manipulation of which is essential for their application as active device elements. However, such manipulation is hindered by lack of microscopic understanding of mechanisms involved in these transitions. A prototypical example is VO2, where previous studies indicated that the MIT resistance change correlate with changes in carrier density and mobility. We studied the MIT using Hall measurements with unprecedented resolution and accuracy, simultaneously with resistance measurements. Contrast to prior reports, we find that the MIT is not correlated with a change in mobility, but rather, is a macroscopic manifestation of the spatial phase separation which accompanies the MIT. Our results demonstrate that, surprisingly, properties of the nano-scale spatially-separated metallic and semiconducting domains actually retain their bulk properties. This study highlights the importance of taking into account local fluctuations and correlations when interpreting transport measurements in highly correlated systems.