By Josh Perry, Editor [email protected]
Researchers from the University of Wisconsin – Madison have developed a new material, based on vanadium dioxide, which transitions from conductor of electricity to nonconductive insulator without changing its atomic structure.
Chang-Beom Eom, right, and Mark Rzchowski inspect a materials growth chamber. (UW–Madison/Sam Million-Weaver)
Because the new material, which is composed of two thin layers of vanadium dioxide with different transition temperatures sandwiched around a sharp interface, does not require a change to its atomic structure the transition is much quicker and makes it ideal for advanced electric switches.
According to an article from the university, researchers “answered a fundamental question that has bothered scientists for years: Can the electronic and structural transition be decoupled — essentially, can the quickly changing electrons break out on their own and leave the atoms behind?”
When the vanadium dioxide sandwich was heated, one layer transitioned to become a metal, while the other layer remained in the insulating structure, but surprised researchers by conducting electricity. Unlike previous attempts at creating this type of material, the Wisconsin researchers created a stable material that can be used in actual devices.
“Key to their approach was the dual-layer, sandwich structure,” the article noted. “Each layer was so thin that the interface between the two materials dominated how the entire stack behaved.”
The research was recently published in Science. The abstract stated:
“The metal-insulator transition in correlated materials is usually coupled to a symmetry-lowering structural phase transition. This coupling not only complicates the understanding of the basic mechanism of this phenomenon but also limits the speed and endurance of prospective electronic devices.
“We demonstrate an isostructural, purely electronically driven metal-insulator transition in epitaxial heterostructures of an archetypal correlated material, vanadium dioxide. A combination of thin-film synthesis, structural and electrical characterizations, and theoretical modeling reveals that an interface interaction suppresses the electronic correlations without changing the crystal structure in this otherwise correlated insulator.
“This interaction stabilizes a nonequilibrium metallic phase and leads to an isostructural metal-insulator transition. This discovery will provide insights into phase transitions of correlated materials and may aid the design of device functionalities.”
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