Yoav Kalchheim

Date: 
Thu, 02/01/2020 - 12:00 to 13:00

The roles of structural, magnetic and electronic degrees of freedom in Mott insulator-metal
transitions
The insulator-metal transition (IMT) in Mott insulators generally involves changes 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 V 2 O 3 , 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 V 2 O 3 and
VO 2 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,
depending on defect properties. 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 allowed us to control the switching mechanism in both materials by focused ion beam
irradiation. 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 field of neuromorphic computation.