For 174 years, nothing happened: And then someone finally noticed.

It would seem that in the modern world, thanks to technology and accumulated scientific knowledge, we have answers to almost everything. Yet such physics, for example, is still full of strange phenomena and mysteries waiting to be discovered. And sometimes it even happens that a theory exists for decades, even centuries, before scientists finally confirm it.

Recently, two phenomena have been observed that take our understanding of physics to a new level.

What exactly are they?

A phenomenon that has been waiting over 170 years to be confirmed

Imagine you have a metal wire, one end of which is hotter than the other. And when an electric current flows through it, the heat is either absorbed or released.

This process was observed as early as 1851 by the British mathematician, physicist and engineer William Thomson, better known as Lord Kelvin. He found that whether a wire heats or cools depends on the direction in which the current flows in relation to the temperature gradient. The phenomenon became one of the three basic thermoelectric phenomena and was aptly named the Thomson effect.

In some materials, such as iron or nickel, its opposite form, the negative Thomson effect, has also appeared. Here, heat propagates against the direction of the current, showing that the behaviour of electrons in different substances can be surprisingly different. For a long time it was assumed that in addition to these longitudinal manifestations, there was also a transverse variant, i.e. a phenomenon running perpendicular to the flow of the current. But observing it has proved extremely difficult – until recently.

An international team of physicists used a semi-metallic mixture, which was subjected to an electric current, a temperature gradient and a magnetic field at right angles. The result was clear evidence of the transverse Thomson effect. It showed that this effect could not only heat or cool the material, but also change the outcome by reversing the direction of the magnetic field. This opens up completely new possibilities for precise and localised temperature control, which is essential for microelectronics or quantum devices, for example.

Quasi-particles that defy logic

Another recent discovery, although in a completely different area of physics, challenges our understanding of physical reality in a similar way to the phenomenon mentioned above.

Back around 2008, theorists suggested that there might be a certain quasi-particle – a formation made up of the collective motion of many particles – that would behave quite unusually. The so-called semi-Dirac fermion was thought to have mass in only one direction. In other words, in one direction it was supposed to move as a massless particle, like a photon, while in another direction it was supposed to be “heavy” and thus subject to the constraints of ordinary matter.

But such an idea seemed almost absurd, since according to special relativity only particles moving at the speed of light can be massless. Once a particle is massive, it cannot exceed that speed. The idea that something could switch between the two states based on the direction of motion seemed almost incompatible with existing physical logic.

That is why it was so crucial when the semi-Dirac fermion was actually demonstrated. For the concept had long been theoretical, but it was recently observed for the first time – and quite by chance – inside a semimetal crystal called ZrSiS, specifically by Yinming Shao and his colleagues at Pennsylvania State University in the US. This discovery not only confirms previous theory, but also provides new avenues in physics or quantum computing and may have diverse practical applications, such as batteries or sensors.

Conclusion

The two examples mentioned above – the transverse Thomson effect and the semi-Dirac fermion – clearly show us that even in areas that seem to be perfectly explored, there are still mysteries waiting for the right researchers and technologies. It’s only a matter of time before scientists come up with a new phenomenon, or a theory is confirmed or refuted…