The Mott insulator-metal transition: structural, magnetic and electronic effects

The insulator-metal transition (IMT) in Mott insulators generally involves transformations in structural, magnetic and electronic degrees of freedom. Disentangling their contributions is of critical importance for understanding their roles in the IMT and developing novel functionalities. We show that in the archetypal Mott insulator V₂O₃, the structural and electronic degrees of freedom are robustly coupled. However, antiferromagnetic fluctuations appear in the vicinity of the IMT both in the insulating and metallic phases, independent of the structural transition. Electronic degrees of freedom were studied by applying current to nanowires of both V₂O₃ and VO₂ which allowed us to disentangle Joule heating and electric field effects. We find that in both materials, IMT-based resistive switching can occur either due to Joule heating or non-thermally. We identify the mechanism behind the non-thermal IMT as doping of the Mott insulator through field assisted carrier generation from defect trap states. This understanding allows us to control the switching mechanism in both materials by defect engineering. The similarity between the field driven IMT in these two very different materials, suggests a universal mechanism for resistive switching in Mott insulators. The ability to induce a non-thermal IMT with ultra-low energy consumption paves the way towards highly energy efficient applications, especially in the emerging field of neuromorphic computation.