At a Glance
- Japanese scientists have successfully observed the first experimental instance of the transverse Thomson effect, a thermoelectric phenomenon first predicted over one hundred years ago.
- Using advanced infrared thermography, the team isolated the effect’s weak signal by subtracting measurements taken with and without a temperature gradient to cancel out competing thermal effects.
- The study revealed that this transverse effect is governed by the Nernst coefficient and its temperature derivative, unlike the conventional effect, which depends on the Seebeck coefficient.
- A key discovery was the ability to switch the material between volumetric heating and cooling simply by reversing the direction of the applied external magnetic field.
- This breakthrough provides a new concept for active thermal management, potentially leading to more efficient and precisely controlled transverse thermoelectric cooling devices for advanced electronics.
Japanese researchers have announced in the journal Nature Physics the first-ever experimental observation of the transverse Thomson effect, a fundamental relationship between heat and electricity that was predicted over a century ago but had never been seen. This phenomenon occurs when a material heats up or cools down in response to an electric current, a temperature difference, and a magnetic field applied at right angles to each other. The discovery, led by scientists from Nagoya University and the University of Tokyo, fills a long-standing gap in physics and confirms a key piece of our understanding of thermoelectricity—the science of converting heat into electrical energy and vice versa.
Observing this subtle effect proved incredibly challenging because it is easily drowned out by other, stronger thermal phenomena. To isolate the signal, the team developed a clever method using advanced infrared imaging. They applied a pulsing electric current to a sample and used an infrared camera to record the resulting temperature changes. By synchronizing their measurements with the current, they could filter out the constant background heat. They then experimented twice—once with a temperature difference across the material and once without—and subtracted the two results, which canceled out a competing phenomenon called the Ettingshausen effect and left behind the pure signal of the transverse Thomson effect.
The experiment revealed a crucial difference between this new effect and its conventional counterpart. While the regular Thomson effect depends on how a material’s voltage-generating ability (its Seebeck coefficient) changes with temperature, this transverse version depends on a different property called the Nernst effect. Specifically, it relies on both the magnitude of the Nernst coefficient and its temperature dependence. This insight led the team to use a bismuth-antimony alloy, a material known to exhibit a large Nernst effect. Remarkably, the researchers found that they could switch the material from heating to cooling simply by changing the direction of the magnetic field, a behavior attributed to two competing components within the effect.
This breakthrough opens a new door to the development of advanced thermal management technologies. The ability to precisely control localized heating and cooling with a magnetic field could lead to more efficient and sophisticated cooling systems, particularly for sensitive electronics. The researchers note that, just as the conventional Thomson effect is used to enhance the performance of cooling devices, this transverse version could achieve the same for a different class of thermoelectric coolers. The next step, they say, is to search for new materials where the components of the transverse Thomson effect work together, rather than canceling each other out, which could unlock even more powerful applications.
References
- Gururaj, T. & Phys.org. (2025, July 16). Scientists achieve first experimental observation of the transverse Thomson effect. Phys.Org; Phys.org. https://phys.org/news/2025-07-scientists-experimental-transverse-thomson-effect.html
- Takahagi, A., Hirai, T., Alasli, A., Park, S. J., Nagano, H., & Uchida, K. (2025). Observation of the transverse Thomson effect. Nature Physics. https://doi.org/10.1038/s41567-025-02936-3
