Local strain inhomogeneities during the electrical triggering of a metal-insulator transition revealed by the x-ray microscopy

TL;DR

This study uses advanced x-ray microscopy techniques to reveal how electrothermal effects induce inhomogeneous strain, lattice distortions, and twinning during the electrical triggering of a metal-insulator transition, even without a structural phase change.

Contribution

It demonstrates that electrothermal MIT triggering causes inhomogeneous strain and lattice distortions, offering new insights into non-equilibrium states in correlated electronic systems.

Findings

Electrothermal MIT triggering results in inhomogeneous strain profiles.

Lattice distortions and twinning are observed during switching.

Strain development differs from equilibrium thermal expansion.

Abstract

Electrical triggering of a metal-insulator transition (MIT) often results in the formation of characteristic spatial patterns such as a metallic filament percolating through an insulating matrix or an insulating barrier splitting a conducting matrix. When the MIT triggering is driven by electrothermal effects, the temperature of the filament or barrier can be substantially higher than the rest of material. Using x-ray microdiffraction and dark-field x-ray microscopy, we show that electrothermal MIT triggering leads to the development of an inhomogeneous strain profile across the switching device, even when the material does not undergo a 1st order structural phase transition coinciding with the MIT. Diffraction measurements further reveal evidence of lattice distortions and twinning occurring within the MIT switching device, highlighting a qualitative distinction between the electrothermal process and equilibrium thermal lattice expansion in nonlinear electrical systems. Electrically induced strain development, lattice distortions, and twinning could have important contributions in the MIT triggering process and could drive the material into non-equilibrium states, providing an unconventional pathway to explore the phase space of strongly correlated electronic systems.