Layered material controls its own conductivity
Researchers have discovered a bilayer 2D crystalline material that is superconducting and ferroelectric, which could have a major impact on next-generation electronics and its capabilities.
Electronics insights
- UW-Madison researchers have discovered a crystalline material that is superconducting an ferroelectric, which could have a major impact for future electronic devices in many different applications.
- This has been a mainstay in general with colleges and universities as they look to find elements and materials that can improve on already existing technology. Much of it is hypothetical, but it can lay the foundation for what we use 10 or 20 years from now.
A University of Wisconsin-Madison engineering team has discovered a bilayer 2D crystalline material that is superconducting and ferroelectric, which could have a major impact on next-generation electronics and its capabilities. An electric current can exist indefinitely in a superconducting material, which has no electrical resistance. A ferroelectric material has a spontaneous electric polarization, and applying an electric field to the material can flip that polarization. Ordinarily, these two unique properties cannot coexist: the electrons that pair up and enable superconductivity preclude any potential polarization.
Synthesized and tested by a team led by Daniel Rhodes, an assistant professor of materials science and engineering at UW-Madison, the material is the first to demonstrate these two properties occurring together. He and his colleagues describe the advance in the January 2023 issue of the journal Nature.
In 2004, researchers synthesized the first 2D material, graphene, by pulling tape off graphite, a material best known as pencil lead. Since then, researchers have developed many other 2D crystals, which are often arranged in a one-atom-thick lattice. Many of these ultrathin materials have novel properties that include superconductivity or ferroelectricity.
In his research, Rhodes investigated the 2D superconductor molybdenum ditelluride (MoTe2). During his time as a postdoctoral researcher at Columbia University, he investigated single layers of molybdenum ditelluride, and discovered that it was a 2D superconductor. However, this time, when he stacked two layers on top of each other, he found that the bilayer molybdenum ditelluride took on new properties. “Not only did it end up being a two-dimensional superconductor, it also ended up being ferroelectric,” he said. “Those two properties have never been seen coupled together in a singular material in the same ground state ever before.”
The two traits interact with one another as well: The ferroelectricity can be a “tuning knob” to control the superconductivity or switch it on and off. “We see the behavior from the ferroelectricity translates to behavior in the superconductivity,” Rhodes said. “And that’s an entirely new concept.”
A University of Wisconsin-Madison engineering team, led by Daniel Rhodes, has discovered a bilayer 2D crystalline material that is superconducting and ferroelectric, which could have a major impact on next-generation electronics and its capabilities. Courtesy: UW-Madison
Rhodes said the basis for superconductivity in the material also appears to be unique. Most superconductivity arises when electrons couple with energy-carrying particles known as phonons. That doesn’t seem to be what’s happening with the bilayer molybdenum ditelluride, but the team is working on a hypothesis to fully explain it. “As far as we can tell, there has to be some pairing interaction between electrons and holes,” Rhodes said, “which is very, very special.”
Rhodes and his team plan to continue work on bilayer molybdenum ditelluride and hope to further explore the interplay between ferroelectricity and superconductivity and how it evolves through various other methods. “This is the first time that we can really see the interplay between ferroelectricity and superconductivity,” Rhodes said. “We’re just really interested in exploring all the consequences that come out of that.”
– Edited by Chris Vavra, web content manager, Control Engineering, CFE Media and Technology, cvavra@cfemedia.com.
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