Spintronics refers to a suite of physical systems which may one day replace many electronic systems. To realize this generational leap, material components that confine electrons in one dimension are highly sought after. For the first time, researchers created such a material in the form of a special bismuth-based crystal known as a high-order topological insulator.

To create spintronic devices, new materials need to be designed that take advantage of quantum behaviors not seen in everyday life. You are probably familiar with conductors and insulators, which permit and restrict the flow of electrons, respectively. Semiconductors are common but less familiar to some; these usually insulate, but conduct under certain circumstances, making them ideal miniature switches. {module INSIDE STORY}

For spintronic applications, a new kind of electronic material is required and it's called a topological insulator. It differs from these other three materials by insulating throughout its bulk, but conducting only along its surface. And what it conducts is not the flow of electrons themselves, but a property of them known as their spin or angular momentum. This spin current, as it's known, could open up a world of ultrahigh-speed and low-power devices.

However, not all topological insulators are equal: Two kinds, so-called strong and weak, have already been created, but have some drawbacks. As they conduct spin along their entire surface, the electrons present tend to scatter, which weakens their ability to convey a spin current. But since 2017, a third kind of topological insulator called a higher-order topological insulator has been theorized. Now, for the first time, one has been created by a team at the Institute for Solid State Physics at the University of Tokyo.

"We created a higher-order topological insulator using the element bismuth," said Associate Professor Takeshi Kondo. "It has the novel ability of being able to conduct a spin current along only its corner edges, essentially one-dimensional lines. As the spin current is bound to one dimension instead of two, the electrons do not scatter so the spin current remains stable."

To create this three-dimensional crystal, Kondo and his team stacked two-dimensional slices of crystal one atom thick in a certain way. For strong or weak topological insulators, crystal slices in the stack are all oriented the same way, like playing cards face down in a deck. But to create the higher-order topological insulator, the orientation of the slices was alternated, the metaphorical playing cards were faced up then down repeatedly throughout the stack. This subtle change in arrangement makes a huge change in the behavior of the resultant three-dimensional crystal.

The crystal layers in the stack are held together by a quantum mechanical force called the van der Waals force. This is one of the rare kinds of quantum phenomena that you actually do see in daily life, as it is partly responsible for the way that powdered materials clump together and flow the way they do. In the crystal, it adheres the layers together.

"It was exciting to see that the topological properties appear and disappear depending only on the way the two-dimensional atomic sheets were stacked," said Kondo. "Such a degree of freedom in material design will bring new ideas, leading toward applications including fast and efficient spintronic devices, and things we have yet to envisage."

An international consortium has been awarded 2 million Euros by the European Commission to develop novel applications that use artificial intelligence (AI) and visual analytics to exploit the vast datasets generated by astrophysics and planetary missions. Over three years, the EXPLORE project will develop these tools on a new virtual platform to create services and enhanced scientific datasets focused on galactic and stellar research, linked to the European Space Agency’s Gaia mission, as well as lunar exploration. The tools will be made available to the community through different cloud science platforms using open source licenses to stimulate uptake and ensure sustainability.

The EXPLORE Consortium is led by the French company, ACRI-ST, and includes eight partners from six countries. The interdisciplinary project brings together astrophysicists, planetary scientists, computer scientists, IT engineers & software developers.

At today’s kick-off meeting, Dr Nick Cox, the EXPLORE Project Coordinator, said: “The sheer volume and increase in complexity of data from space science missions, as well as the need to combine multiple data sets, requires an increase in both data management and processing capabilities. AI-based solutions and interactive visualization techniques for big data are not just useful tools to explore the Universe but are becoming a necessity.” {module INSIDE STORY}

EXPLORE will develop six scientific data applications to test methodologies and tools for space data exploitation on a collaborative cloud environment, the EXPLORE Thematic Exploitation Platform (EXPLORE-TEP).

Rather than focus on one main scientific topic, EXPLORE aims to foster synergies between different areas of space science. Four of the applications will leverage data primarily from Gaia, supplemented with data from other surveys, developing tools to help understand the evolution of our galaxy, the 3D distribution of interstellar matter, as well as to support the discovery, classification, and characterization of stars. The remaining two applications will integrate data from a range of international lunar missions to focus on the characterization of the Moon’s surface and potential human landing sites. A key objective will be to facilitate the integration and visualization of multiple datasets.

Prof Dovi Poznanski of Tel Aviv University, who leads EXPLORE’s AI methodology development, said: “By putting together different experiences and backgrounds we introduce diversity and interdisciplinarity in the analysis of space science data. Today’s big datasets in imagery, spectroscopy, and 3D mapping require sophisticated tools. However, there are common basic principles among the different fields, which means there is a vital need for cross-fertilization if we want to optimize the most advanced tools.”

EXPLORE-TEP builds on the heritage of a platform designed by ACRI-ST and funded by ESA to facilitate and expand the use and uptake of Copernicus-Sentinel Earth Observation mission data.

Dr Jeronimo Bernard-Salas, of ACRI-ST and Deputy Coordinator of EXPLORE, said: “For astronomers, it is becoming increasingly difficult to simply download all the data to their desktop and use their favorite analysis tools locally. Through EXPLORE, we aim to bring processing and analysis capabilities, accessible via existing and new collaborative working environments, to the data. This allows any user to exploit space mission and supporting ground-based data more efficiently and to effectively share their methods and results, thus ensuring science becomes more open.”

Ultimately, EXPLORE aims to apply the tools to other areas of space science, as well as to map business opportunities for potential market entry in other domains.