Physicists have observed a strange new type of transition in electronic crystals

(ORDO NEWS) — As basic science teaches us, changes in temperature can lead to phase transitions in materials—for example, when water solidifies into ice in the cold.

However, in some cases, the temperature causing the change is different depending on whether the material is being cooled or heated. This is known as a hysteresis loop, and the researchers believe they have discovered a strange and completely new example of this phenomenon.

It’s not the kind of transition you’ll see in everyday life, requiring a multi-layer composite crystalline solid called EuTe4, huge temperature ranges, and a kilometer-long track to launch fast-moving charged particles deployed to create bright laser light.

Using such a laboratory setup, the scientists observed that the hysteresis loop for EuTe4 covered a gigantic temperature range of at least 400 degrees Kelvin – much larger than the usual range for such a crystalline solid, which is typically no more than tens of degrees Kelvin.

The research got more and more interesting. There were no changes in the electronic or lattice structure of the material over the measured temperature range, which again is not in line with how phase transitions should occur in crystals.

While this discovery is just beginning, the team has a few ideas about what might be happening: the way the electrons are arranged in EuTe4 causes a secondary electron crystal to form, and it could be that as this second layer moves and shifts, it creates various configurations in the hysteresis loop.

Further experiments showed that the researchers were able to significantly change the electrical resistance of the material by cooling or heating the crystals – another indication that something strange and unexpected was happening.

This opens up a whole range of possibilities. One way scientists can use this is to measure the electrical resistance of EuTe4 at room temperature and then determine the lowest or highest temperature the material has experienced before due to this “thermal memory.”

The work done here could be extended to study other solids and how they change when exposed to extreme temperature ranges, the team says. This could be especially promising in terms of gaining more control over the materials used in switches and memory in computers.

First, further research is needed. The researchers suspect that there is more to discover beyond the 400 Kelvin range – it was as far as their setup would allow. After further analysis, the hysteresis can be controlled in other ways besides changing the temperature.


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