Feb 28 2019
Taking a major stride forward in a research field that was awarded the 2016 Nobel Prize in Physics, an international research team has discovered that topological materials—substances that have strange electronic behaviors—are actually very common, and include usual elements such as gold and arsenic.
The researchers created an online catalog to enable new topological materials to be easily designed using elements from the periodic table.
These materials have unpredictable and exotic properties that have transformed the understanding of scientists of how electrons behave. Researchers are hopeful that these substances could turn out to be the basis of futuristic technologies, such as quantum computing and low-power devices.
Once the analysis was done and all the errors corrected, the result was astonishing: more than a quarter of all materials exhibit some sort of topology. Topology is ubiquitous in materials, not esoteric.
B. Andrei Bernevig, Professor of Physics, Princeton University
Bernevig is a senior author of the paper.
Topological materials are fascinating since their surfaces have the ability to conduct electricity without any resistance, making them more energy efficient and potentially faster compared to the existing technologies. They are named after an underlying theory that draws on topology—a branch of mathematics describing objects based on their potential to be stretched or bent.
The basis of the 2016 Nobel Prize in Physics, shared among Princeton University professor F. Duncan Haldane, the Sherman Fairchild University Professor of Physics, J. Michael Kosterlitz of Brown University, and David J. Thouless, University of Washington-Seattle, was the beginning of the theoretical understanding of these states of matter.
To date, only a few hundred of the over 200,000 familiar inorganic crystalline materials have been characterized as topological, and they were imagined to be anomalies.
When fully completed, this catalog will usher in a new era of topological material design. This is the beginning of a new type of periodic table where compounds and elements are indexed by their topological properties rather than by more traditional means.
B. Andrei Bernevig, Professor of Physics, Princeton University
The international team included scientists from Princeton; the Donostia International Physics Center in San Sebastian, Spain; the IKERBASQUE Basque Foundation for Science; the University of the Basque Country; École Normale Supérieure Paris and the French National Center for Scientific Research; and the Max Planck Institute for Chemical Physics of Solids.
The researchers analyzed nearly 25,000 inorganic materials with atomic structures that are experimentally known with accuracy, and classified in the Inorganic Crystal Structure Database. The study outcomes demonstrate that in contrast to being rare, over 27% of materials in nature are topological.
The team made the newly developed online database available at www.topologicalquantumchemistry.com. It enables users to choose elements from the periodic table to develop compounds that can be explored by the user for its topological characteristics. At present, more materials are being investigated and placed in a database to be published later.
The complicated task of topological classification of the 25,000 compounds was enabled by two factors.
First, two years earlier, a few of the present authors proposed a theory, called topological quantum chemistry, published in Nature in 2017, which enabled the topological characteristics of any material to be classified from the simple understanding of the nature and positions of its atoms.
Second, in this study, the researchers used this theory on the compounds in the Inorganic Crystal Structure Database. By doing this, the authors had to create, write, and modify a large number of computerized instructions to compute the energies of electrons in the materials.
“We had to go into these old programs and add new modules that would compute the required electronic properties,” stated Zhijun Wang, a professor at the Beijing National Laboratory for Condensed Matter Physics and the Institute of Physics, Chinese Academy of Sciences, who was a postdoctoral research associate at Princeton.
We then needed to analyze these results and compute their topological properties based on our newly developed topological quantum chemistry methodology.
Luis Elcoro, Professor, University of the Basque Country, Bilbao, Spain
The researchers wrote multiple sets of codes that acquire and analyze the topology of electrons in real materials. They have rendered these codes available to the public through the Bilbao Crystallographic Server. The team ran its codes on the 25,000 compounds using the Max Planck Supercomputer Center in Garching, Germany.
Computationally, it was pretty incredibly intensive stuff. Fortunately, the theory showed us that we need to compute only a fraction of the data that we needed previously. We need to look at what the electron ‘does’ only in part of the parameter space to obtain the topology of the system.
Nicolas Regnault, Professor, École Normale Supérieure, Paris
Regnault is also a researcher at the French National Center for Scientific Research.
“Our understanding of materials got much richer because of this classification,” stated Maia Garcia Vergniory, a researcher at Donostia International Physics Center in San Sebastian, Spain. “It is really the last line of understanding of properties of materials.”
Earlier, Claudia Felser, a professor at the Max Planck Institute for Chemical Physics of Solids in Dresden, Germany, had predicted that even gold acts topological. “A lot of the material properties that we know—such as the color of gold—can be understood through topological reasoning,” stated Felser.
Currently, the researchers are making efforts to classify the topological nature of additional compounds in the database. Further steps would be to identify the compounds with the most ideal conductivity, versatility, and other properties, as well as to experimentally verify their topological nature. “One can then dream about a full topological periodic table,” stated Bernevig.