Electrically steered conduction topologies and period-doubling phase dynamics in VO2

TL;DR

This study visualizes and analyzes the nanoscale phase transition dynamics in VO2 induced by electric fields, revealing mechanisms for ultrafast, reconfigurable electronic topologies relevant for next-generation devices.

Contribution

The paper introduces a novel ultrafast transmission electron microscopy technique to directly observe electric-field-driven phase transitions in VO2 at nanoscale and sub-nanosecond scales.

Findings

Electric-field-induced Poole-Frenkel emission localizes and triggers the Mott transition.

Reconfigurable connectivity topologies bypass thermal limits due to non-linear PF effects.

Coupling of thermal and elastic energies causes step-wise and period-doubling domain evolution.

Abstract

The insulator-to-metal transition (IMT) in strongly correlated materials, such as vanadium dioxide (VO2), offers a transformative platform for next-generation adaptive electronics and neuromorphic computing. However, harnessing this non-equilibrium phase transition for deterministic device operation is fundamentally hindered by the inability to disentangle electric-field effects from Joule heating, owing to a lack of operando techniques capable of resolving phase dynamics at nanoscale spatial and sub-nanosecond temporal scales. Here, using a newly developed electrical-pulse-pump ultrafast transmission electron microscope (E-UTEM), we directly visualize the multi-scale electro-thermo-mechanical dynamics of the IMT in suspended VO2 devices. Our results reveal that electric-field-induced Poole-Frenkel (PF) emission, localized by patterned oxygen vacancies, plays a decisive role in redistributing the internal electric field to trigger a deterministic Mott transition. The extreme non-linearity of this PF effect enables the formation of dynamically reconfigurable connectivity topologies that bypass conventional thermal limits. Furthermore, we observe that the coupling of thermal and elastic energies governs a discrete domain evolution, characterized by step-wise and period-doubling configurational resets, which is a hallmark of non-equilibrium phase dynamics in constrained geometries. By integrating experimental imaging with phase-field simulations, we establish a comprehensive framework for the electrically-driven IMT and predict sub-100-ps switching kinetics. These findings provide a fundamental basis for the rational design of ultrafast, low-energy functional devices through nanoscale defect and strain engineering in correlated systems.