Joseph Heremans is used to making discoveries that “look a bit like magic.” He discovers unexpected properties in materials and figures out how to use heat to generate electricity in ways that once seemed only theoretical.
With a new federal scholarship that finances the research projects of professors with permanent teaching assignments, Hiermann’sProfessor for Mechanical and aerospace engineering at Ohio State University and a prominent scholar of nanotechnology in Ohio, will once again set out to prove something revolutionary about heat, spin and electricity.
Heremans is one of eleven university scientists nominated for the class of 2024. Vannevar Bush Faculty ScholarshipThe Ministry of DefenseThe premier individual investigator award for basic research. He is the first Ohio State faculty member to be selected for the fellowship.
“I am delighted to have Professor Heremans lead this ambitious work at Ohio State University,” said Walter “Ted” Carter Jr., President of Ohio State University. “Buckeyes are at the forefront of research and innovation that is having a significant impact on the world, and this Department of Defense grant provides an exciting opportunity to contribute to U.S. global leadership in security technology.”
With funding of about $3 million over five years, Heremans will focus almost exclusively on polarization caloritronics, replacing ferromagnets with ferroelectric materials in potential spintronics-like applications.
“It’s like a new beginning,” said Heremans, also a professor of Materials science and engineering And physics“It’s fantastic to have an established career in research behind you and then suddenly have the opportunity to go in a completely new direction. It’s refreshing.”
“Bindu Nair, director of the Basic Research Office of the U.S. Department of Defense, specifically told me to take big risks in the research funded by this program.”
The Ministry of Defense Basic Research Unit The grant sponsor, who sponsors the fellowship, received 170 white papers for this year’s competition. Expert panels invited 27 proposals for finalization, from which the 11 fellows were recommended.
“The idea has to be extremely ambitious, and yet the proposal has to provide enough preliminary data to prove it’s possible,” Heremans said. “It doesn’t have to build on what you’ve done before – it’s based on the fact that you’ve delivered in the past, but you’re not bound by your past now. You can come up with new ideas and try them out.”
In early 2023, Heremans and a graduate student in his lab, Brandi Wooten, led the work behind a Paper In it, they predicted and confirmed theoretical properties of solid materials called ferroelectrics – hinting at the possibilities Heremans will pursue during the fellowship.
Spintronics takes advantage of electron spin in materials known as ferromagnets. In these materials, the atoms behave like tiny magnets, all aligning with each other to form a large magnet with a magnetic “moment” that creates a magnetic field around itself. Magnons, or spin waves, are the way these tiny magnets move in relation to each other, similar to how a crowd does “the wave” at a football game.
Heremans’ team spent over a decade studying the propagation of spin waves under the influence of temperature differences. Heremans is now turning his attention to another class of materials, the so-called ferroelectrics – materials that contain both positively and negatively charged atoms (ions).
At the atomic level, strong local electric fields develop between these ions. Similar to the way the tiny magnets in ferromagnets are aligned, these local electric fields align with each other to form a ferroelectric material with a net polarization moment.
The team hypothesized that the quasiparticles moving in wave-like patterns in ferroelectrics are the vibrations of the atoms themselves, called phonons. Preliminary data show that these phonons carry enough heat to change the thermal conductivity of the materials when an external electric field is applied. This led the team to believe that since spin waves carry a spin current, the new quasiparticles in ferroelectric materials should carry a polarization current – a completely new concept.
In this new work, Heremans explores the theory that the flow of electric polarization – without the need for a magnetic field – can be detected experimentally and used for engineering functions similar to spin currents: controlling heat flow, generating electricity from heat, and transporting information about a thousand times faster than magnetic spins can.
Several classes of applications could follow.
“Basically, you can use polarization currents as a heat engine. Second, you can modulate heat conduction through a solid with an electric field, which allows you to create the thermal equivalent of a transistor,” Heremans said. “Third, and the most ambitious, would be devices with a logic memory based not on magnetic spin waves but on polarization currents. They would consume less electricity, heat up less, and would not require large power plants to run data centers.”
One advantage for the military is the ability to minimize electromagnetic interference – especially enemy attempts to jam communications signals, he added.
Heremans has been receiving funding from the U.S. Department of Defense since 2010, but this opportunity is special for him. He says it puts him in the “who’s who” of experts doing relevant work for the Department of Defense.
“It really is a chance to let your imagination run wild.”
