X-ray Nano-imaging of a Heterogeneous Structural Phase Transition in V2O3
arxiv(2024)
Abstract
Controlling the Mott transition through strain engineering is crucial for
advancing the development and application of memristive and neuromorphic
computing devices. Yet, Mott insulators are heterogeneous due to intrinsic
phase boundaries and extrinsic defects, posing significant challenges to fully
understanding the impact of local microscopic distortions on the local Mott
transition, which demands structural characterizations at the relevant length
scale. Here, using a synchrotron-based scanning X-ray nanoprobe, we studied the
real-space structural heterogeneity during the structural phase transition in a
V2O3 thin film, with a resolution of 30 nm. Through temperature-dependent
metal-insulator phase coexistence mapping, we report a variation in the local
transition temperature of up to 7 K across the film and the presence of the
transition hysteresis at the nanoscale. Furthermore, a detailed quantitative
analysis demonstrates that the spatial heterogeneity of the transition is
closely tied to the tilting of crystallographic planes in the pure insulating
phase. We develop a structural model allowing us to interpret these tilts as
variation of the monoclinic distortion during the rhombohedral-monoclinic phase
transition. Our work highlights the impact of local heterogeneous lattice
distortions on the Mott transition and lays the groundwork for future
innovations in harnessing strain heterogeneity within Mott systems for the
next-generation computational technologies.
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