Ionothermoelectric cooling; lead-free ferroelectrics; electrical signals from magnons.
Researchers from the University of Osaka, University of Tokyo, and Japan’s National Institute of Advanced Industrial Science and Technology proposed an ionothermoelectric cooling strategy for chips that enhances cooling by driving the flow of ions through nanoscale channels.
“We fabricated a nanosized pore in a semiconductor membrane and surrounded the nanopore with a ‘gate’, in the form of a nanowire. Applying a voltage to the gate induced the flow of ions through the nanopore,” said Makusu Tsutsui, an associate professor at the University of Osaka, in a statement. “Varying the voltage modulated the surface charge of the nanopore.”
The approach is analogous to the Peltier technique. A negative applied voltage resulted in a negatively charged nanopore that was only permeable to positively charged ions (cations). Each ion drags a certain quantity of heat along with its charge. To demonstrate the technique, the team created a concentration gradient in saltwater around the nanopore to drive cation transport in one direction, pumping heat out of the nanopore. Reversing the applied voltage made the nanopore surface positive and permeable only to negative ions (anions) and switched the system from cooling to heating.
“We placed a nanoscale thermocouple next to the holes within the materials – or nanopores – to map temperature changes driven by the voltage-induced ion transport,” said Tomoji Kawai, a professor at the University of Osaka, in a statement. “Switching from heating to cooling resulted in temperature drops of over 2 K. We found that the ionic heat transfer depended on the input power as well as the ion species used.” [1]
Researchers from the University of Arkansas, North Carolina State University, Cornell University, Drexel University, Stanford University, Pennsylvania State University, Argonne National Laboratory, and Oak Ridge National Laboratory created a lead-free ferroelectric material that can be used through epitaxial strain, rather than chemical tuning.
The team grew a thin film of sodium niobate (NaNbO3), a lead-free ferroelectric material with a complex crystalline ground state structure at room temperature, on a strontium titanate substrate. Strain is created when the atomic structure of sodium niobate contracts and expands as it tries to match the substrate’s structure. The strain caused the sodium niobate to exhibit three phases simultaneously, optimizing the material’s useful ferroelectric properties by creating more boundaries.
“What is quite remarkable with sodium niobate is if you change the length a little bit, the phases are changing a lot,” said Laurent Bellaiche, distinguished professor of physics at the University of Arkansas, in a press release. “What I was expecting, to be honest, is if we change the strain, it will go from one phase to another phase. But not three at the same time. This was an important discovery.”
This work was conducted at room temperature. Next, the researchers plan to investigate whether sodium niobate responds to strain in the same way at extreme temperatures ranging from -270 °C to 1,000 °C. [2]
Researchers from the University of Delaware and University of Maryland used computer simulations to explore how magnons behave in antiferromagnetic materials and discovered that the movement of magnons can produce detectable electric signals.
“The results predict that we can detect magnons by measuring the electric polarization they create,” said Matthew Doty, professor in the Department of Materials Science and Engineering at UD’s College of Engineering, in a statement. “Even more exciting is the possibility that we could use external electric fields, including those of light, to control the motion of magnons. Future devices that replace conventional wires with magnon channels could send information much faster and with much less wasted energy.”
“We developed a mathematical framework to understand how orbital angular moment contributes to magnon transport. We discovered that when the magnon orbital angular moment interacts with the atoms in the material, it produces an electric polarization,” said D. Quang To, a postdoctoral researcher at UD’s Center for Hybrid, Active and Responsive Materials, in a statement. “Our framework provides a powerful tool that will allow the research community to predict and manipulate the behavior of magnons.”
The researchers are now conducting experiments to verify the predicted effects and plan to explore how magnons interact with light to determine whether the orbital angular moment of light can be used to control the transport or detection of magnons. [3]
[1] M. Tsutsui, K. Yokota, W.-L. Hsu, et al. Gate-Tunable Ionothermoelectric Cooling in a Solid-State Nanopore. ACS Nano Article ASAP. https://doi.org/10.1021/acsnano.5c13339
[2] R. Ghanbari, H. KP, K. Patel, et al. Strain-induced lead-free morphotropic phase boundary. Nat Commun 16, 7766 (2025). https://doi.org/10.1038/s41467-025-63041-w
[3] D.Q. To, F. Garcia-Gaitan, Y. Ren, et al. Magnon-induced electric polarization and magnon Nernst effects, Proc. Natl. Acad. Sci. U.S.A. 122 (43) e2507255122, https://doi.org/10.1073/pnas.2507255122
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