Physicists have recently observed a phenomenon that was predicted over 170 years ago. This is significant because it could lead to more precise ways of controlling heat in small spaces, which is important for many precision applications. The team published their findings in Nature Physics.

In 1851, physicist William Thomson (also known as Lord Kelvin) noticed that when an electric current runs through a conductor that has a temperature gradient, the material either releases or absorbs heat depending on the direction of the current.

This was one of the early thermoelectric effects, connecting heat and electricity, and was found in metals such as copper, zinc, and silver. The exact change depends on a value called the Thomson Coefficient. A negative version of the effect was also seen in metals like iron, where heat behaves in the opposite way relative to current flow.

Scientists had long suspected another version was hiding in plain sight. This version would occur at right angles to current flow, but it was not confirmed until now.

By using a semimetal made of bismuth and antimony, researchers were able to apply current, temperature difference, and a magnetic field in perpendicular directions to each other. Picture a flat sheet where electric current flows from left to right, heat is applied from one side, and a magnetic field comes from above. In this setup, they could heat or cool the sheet by flipping the magnetic field direction.

Scientists noticed uneven temperature changes along the edges of the material but saw smooth rises or falls inside the sheet. The edge behavior came from the Ettingshausen effect, which acted more strongly there even without a temperature gradient.

The team calculated that this Transverse Thomson Effect is roughly 15 percent as strong as the original Thomson effect. They think it could be even stronger in other materials.

The Thomson Effect depends on how electrons are packed differently between cooler and warmer parts of a material. As electrons move, they absorb or release energy. Remember, this is not the same as the better-known Joule Thomson Effect, which involves gases instead of solids.

By discovering the Transverse Thomson Effect, scientists now have a new tool. It could be used in technologies where accurate and localized temperature control matters, possibly transforming thermal design in small-scale applications.

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