Research Highlight

Model shows when an insulator becomes a conductor

doi:10.1038/nindia.2021.112 Published online 17 August 2021

The presence of impurities or defects, also known as disorder, in a metal could hinder the flow of free electrons. Beyond a critical value, such disorder could completely stop electron flow, turning the metal into an insulator.  

A model developed by physicists from the Indian Institute of Technology in Guwahati has now shown that increasing the disorder strength beyond a specific value could make an insulator re-enter a metallic or a conducting state1.

This finding, the researchers say, not only contradicts the fundamental understanding of metal-insulator transition but has also opened up a new direction for research involving fundamental physics.

The researchers, led by Saurabh Basu and Tapan Mishra, based their model on a one-dimensional dimerised lattice of a metal or a conductor. This model allowed them to gain insights into the behaviour and flow of electrons in the lattice.

Beyond a critical value, disorder arrested electron flow in the lattice, making it an insulator. A further increase in disorder strength, supported by some kinetic energy, initiated electron flow, turning the insulator into a conductor again.

Such a transition gave rise to a critical state that was neither a perfect metal nor a perfect insulator. It was not the same metal at zero disorder strength, the researchers explained.

The findings could, in principle, be simulated in quantum gas experiments in which atoms at temperatures close to absolute zero and extremely low pressures could mimic the behaviour of electrons in a one-dimensional lattice, said lead author Shilpi Roy.


References

1. Roy, S. et al. Reentrant localization transition in a quasiperiodic chain. Phys. Rev. Lett. 126, 106803 (2021)