Nanotechnology

Finds band topology features in amorphous thin films

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June 30, 2023

(Nanowerk News) In recent years, scientists have studied a special material called topological material, paying special attention to shape, that is topology, its electronic structure (electronic band). Although invisible in real space, their unusual shape in topological materials yields a variety of unique properties suitable for building next-generation devices.

It is thought that in order to exploit the physical properties of topology, a crystalline material is needed, in which the atoms are highly ordered and arranged in a repeating pattern. Materials in the amorphous state, that is, in which the atoms are disordered and only periodically arrange over short distances, are considered unsuitable to accommodate the extraordinary physical properties of topological materials. amorphous thin films Amorphous thin films were tested in this study. (Image: Tohoku University)

Now, a collaborative research group has verified that even amorphous materials can have this special property. The group is led by Associate Professor Kohei Fujiwara and Professor Atsushi Tsukazaki of Tohoku University’s Institute for Materials Research (IMR); Lecturer Yasuyuki Kato and Professor Yukitoshi Motome of the Graduate School of Engineering at the University of Tokyo and Associate Professor Hitoshi Abe at the High Energy Accelerator Research Institute for the Science of Material Structure.

Details of their findings are reported in the journal Nature Communications (“Berry curvature contribution of the kagome-lattice fragments in amorphous Fe-Sn thin films”).

“We found that the concept of band topology, which has been discussed mainly in crystals, is also valid and technologically useful in the amorphous state,” said Fujiwara. a Character space of real numbers and contrasting wavenumbers of crystalline and amorphous thin films The contrast of the real and wave number space characters of crystalline and amorphous thin films. (Image: Tohoku University)

To make their discovery, the team performed experiments and model calculations on iron-tin amorphous thin films. They demonstrated that despite the short-range atomic arrangement, amorphous materials still exhibit the same special effects as crystalline materials, especially the anomalous Hall effect and Nernst effect.

“Amorphous materials are easier and cheaper to manufacture compared to crystals, so this opens up new possibilities for developing devices using these materials. This could lead to advances in sensing technology, which is important for creating an Internet of Things (IoT) where many devices connected and communicate with each other,” added Fujiwara.

Going forward, the group is eager to explore more amorphous materials and develop innovative devices that use them.



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