Daniel Rhodes, an assistant professor in the Department of Materials Science and Engineering at the University of Wisconsin-Madison, has been awarded a prestigious Presidential Early Career Award for Scientists and Engineers (PECASE) from the U.S. Army Combat Capabilities Development Army Research Laboratory.
The five-year, $1 million award is aimed at incentivizing early career university faculty to pursue fundamental research in areas that could have significant impact on Army operational capabilities and related technologies.
Rhodes’ proposal is also under consideration for the White House Honorary PECASE award—the highest honor bestowed by the United States government on researchers who show exceptional promise in their fields.
Rhodes is an expert on the synthesis and processing of novel two-dimensional (2D) and bulk materials which exhibit interesting correlated, superconducting and multiferroic phenomena. In his PECASE project, Rhodes proposes to study a type of material called quantum spin Hall insulators, which are part of broader class called topological materials. These materials could enable new types of transistors for faster, more efficient digital devices.
Conventional silicon transistors—the switches that flip on or off at the heart of computer processors and other digital devices—face a fundamental physical limit called “Boltzmann’s Tyranny.” The transistors require a certain voltage to produce enough current to flip the switches, which leads to excess thermal loss, or heat. Even the best silicon transistors can have substantial limits on their power efficiency.
Rhodes, however, thinks that these new materials could be used to produce transistors that overcome Boltzmann’s Tyranny. “For these quantum spin Hall insulators, if you could make them switchable at room temperature, you wouldn’t have the tremendous heat losses that you have with silicon transistors and interconnects,” says Rhodes. “You’d be able to achieve way higher transistor speeds.”
Currently, only materials cooled to extreme temperatures exhibit quantum spin Hall insulator properties. “The record right now is 100 degrees Kelvin (-280 degrees Fahrenheit),” says Rhodes. “But theoretically, there’s no limitation on why this phenomenon can’t survive at room temperature, and we want to find one of these materials.”
The other issue with these materials is that the insulator state does not survive over long distances (at least on the nanoscale), fading after 100 nanometers, which is one thousand times smaller than the width of a human hair. Rhodes has realized that this is likely due to defects in the material. In his project, he plans to study these materials to understand how such defects affect the quantum spin Hall insulator phenomenon.
This, he hopes, will then enable him to develop techniques to synthesize even cleaner versions of the material that can enable the phenomenon over distances meaningful for producing electronic devices.
The PECASE funding will allow Rhodes to purchase new furnaces for his lab and help his team perform new types of analysis on these materials. It will also allow his lab to push topological materials further than previous efforts. “Since it’s such a long-duration award, we’ll hopefully be able to introduce new topological materials into the community and broaden the 2D materials playground,” he says.
Earning the PECASE, says Rhodes, is a sign that his research and innovations are valued by the 2D materials community. “I’m also very grateful for the program manager who gave me this opportunity. This was a long effort and ongoing conversation between us over many years that coalesced into this proposal. And it’s great that it worked out,” he says. “It really shows the value of collaborating with the Department of Defense labs in developing your individual research program, which is partly what led to this funding.”
Top image by Joel Hallberg