MOSCOW, August 29. / TASS/. Researchers from the Tomsk Polytechnic University in collaboration with colleagues from the US, China, and Germany observed an unusual self-organization of atoms in the inner volume of nanoparticles and learned to control it with the help of an electric field.

Similar "controllable" nanoparticles might be useful for creating high-capacity independent memory, quantum computers, and other electronic devices of the future.

"Our results prove that in nanoparticles, a small displacement of all atoms takes place. From a distant glance, the displacement has a pronounced twisting feature and therefore is designated as a topologic vortex. That said, the core of the vortex can be described as a nanostem which may be displaced by the field, wiped away, and again restored inside nanoparticles," said Edwin Fohtung, one of the study’s co-authors, and Professor at Los Alamos National Laboratory and New Mexico State University.

The scientists’ study described in a research article was recently published in the magazine, Nature Communications, with the first author of the work being an engineer from TSU’s Department of General Physics Dmitry Karpov.

What are topologic defects and why is it essential to study them?

In the modern material science, the defects of substances are classified into two large groups. The first is composed of traditional, well-described defects where the order of atoms in the substance are distorted mechanically, that is, some atoms are deleted or inserted into the crystal lattice. In the second, there are no pronounced local changes. Instead, the way the lattice’s space is arranged is changed and therefore such defects are called topological.

Such topological defects can strongly influence the substance and give it various special properties as superfluidity or superconductivity. For this reason, it is of great practical importance for material sciences to explore these defects. That said, topological defects exist only in low-dimension materials: 2D nanostems, nanofilms (layers of a thickness of several atoms), 1D nanodots, and materials with a high ratio of surface area to the volume of the substance of nanoparticles (spherical particles composed of several dozens or hundreds of similar atoms). One of the most important topologic defects is the topologic vortex.

How did scientists spot the structure of nanoparticles?

In the research experiment, scientists studied the nanoparticles of barium titanate, whose internal structure was visible with penetrating X-rays of a synchrotron source, Advanced Photon Source (Chicago, USA). The researchers obtained the image from the volume of nanoparticles with a resolution of 18 nanometers which made it possible to analyze miniscule changes in the structure. As a result, the researchers demonstrated that when exposed to external electrical fields, the core of the topologic vortex inside the nanoparticles is displaced, while de-excitation leads to the restoration of the core position.

New electronics

The researchers’ discovery of the possibility to control and regulate topologic vortices in nanoparticles is essential for creating new electronics.

The thing is that modern components of electronics become smaller and smaller and slowly approaching the bottommost limit which if broken through would seriously drive down the efficiency of devices due to various quantum effects. To overcome this limitation, several approaches have been suggested.

One of the perspective directions is to make use of topologic vortices. For instance, based on such vortices, one can design volatile memory units with a high density of information storage and quantum computers where the data will be encoded as characteristics of topologic vortices.

"Further research using diffraction of synchrotron radiation on the low-dimension materials will enable a better understanding of mechanisms of controlling and restoring various topologic defects. At this point, the new challenge for engineers is how to manage and to apply learned lessons to solve the most pressing problems concerning electronics of the future."