A particle that changes its behavior depending on the direction it takes: in one sense, it glides effortlessly as if it weighs nothing. In the other, she seems to have weight. This might sound like a concept straight out of the science-fictionbut this is what researchers have just observed for the first time. These particles, called fermions semi-Diracseem to contradict the classical laws of physique and could transform the field of materials and their technological applications.
Credit: Yinming Shao / Penn State.
The discovery took place in a semi-metallic material with unique properties: ZrSiSa crystal composed of zirconiumsilicon and sulfur. This material has a layered structure, comparable to that of graphite or the famous graphenean ultrathin material. During a series of experiments where he was exposed to a magnetic field powerful and infrared rays, the electrons inside the crystal began to behave in completely unexpected ways. The researchers then understood that they were dealing with a very particular particle: semi-Dirac fermions.
Semi-Dirac fermions have a strange characteristic: depending on the direction in which they move, they sometimes appear massless, sometimes “weighted”. To image this phenomenon, scientists compare it to a train traveling at full speed on a fast track. As long as he stays in a specific direction, nothing seems to be able to stop him. But if it changes direction, it encounters resistance and feels like it is slowing down, as if it is becoming heavier. This alternation between a “massless” state and a “with mass” state had never been observed in this way until now.
It was Yinming Shao, the researcher at the head of this study, who carried out these experiments with his team. Originally, their goal was simply to study the response of ZrSiS electrons when subjected to an increasing magnetic field and light infrared. But as conditions became more extreme, unusual behavior began to appear. This phenomenon led to the identification of semi-Dirac fermions, confirming a theoretical prediction more than ten years old.
This discovery could well open a new era for materials science. By better understanding these semi-Dirac fermions, it would be possible to design materials with exceptional properties, capable of revolutionizing several technological fields. For example, materials inspired by ZrSiS could make it possible to manufacture electronic components that are thinner, faster and more efficient. We are thinking in particular of new generation batteries, capable of storing moreenergy in a small space, or even to ultrasensitive medical devices.
One of the interesting features of ZrSiS is its layered structure, which makes it easier to study and manipulate. By isolating ultrathin layers, as has been done with graphene, researchers hope to be able to explore the surprising properties of semi-Dirac fermions in more detail. This approach could make it possible to exploit these particles to create new technologies, such as more efficient quantum computers or sensors capable of detecting infinitesimal variations in their environment.
Although this progress marks an important step, many questions remain. Why do these semi-Dirac fermions behave like this? What other surprises could they have in store for researchers? And above all, how can we use them effectively for concrete applications? So many mysteries that physicists are now striving to resolve.
The discovery of semi-Dirac fermions illustrates once again how materials physics is constantly evolving. This strange phenomenon, observed for the first time in ZrSiS, could well shake up our current knowledge and open the way to innovations that we still struggle to imagine. The next few years will be decisive for understanding the potential of these particles and seeing how they could, ultimately, improve our everyday technologies. This scientific advance, as mysterious as it is impressive, reminds us that matter has not yet revealed all its secrets.
