Topological metals have “foreign” properties, and their size is proportional to a parameter called Chern number. Now, this is the first time that chiral crystals of palladium and gallium have been used to obtain the maximum value through experiments.
This Topology This is a part of mathematics, which is used to study the properties of geometry that will not change during the transformation process. This branch of science can also describe how very fine materials gradually undergo strange changes controlled by quantum laws.
In this field, theoretical physicists David Thouless, Duncan Haldane and Michael Kosterlitz were awarded the 2016 Nobel Prize in Physics. Because they open the door to “the unknown can adopt an abnormal state.”
The recognition is due to his discovery of the topological transformation and topological stage of matter, which is a very subtle phase change at the microscopic level, which produces a unique electronic phenomenon. In the physics of condensed matter, it has applications in data management in the following areas: Electronic Component And in Quantum computing.
inside Topological metals, The behavior of electrons is different from that of traditional materials. The magnitude of the strange phenomenon they exhibit is proportional to the number called Chen Shu.
In other words, the basic feature that determines the topological structure of a metal is the characteristic of electrons, that is Chen Shu. For regular metals, its value is zero, but how big is it?
Chiral crystals of palladium and gallium
In order to answer this question, a team of international researchers is now using materials Palladium Gallium (PdGa) Chiral Crystal.
Chirality is an attribute of an object and cannot be superimposed with its mirror image like our hands. In this case, the researchers managed to grow crystals with different chirality, which affected the electronic properties of the material. Therefore, they managed to obtain the largest Chern number through experiments, but with opposite signs (+4 and -4).
In the research, the journal published the journal science, Ikerbasque Physics from Donostia International Physics Center (DIPC) has participated Maya García (Maia García Vergniory) And DIPC physicist Ikerbasque Fernando de Juan.
Fernando de Juan pointed out: “So far, it has not been possible to prove that any substance reaches the maximum Chen’s number (+4)”, “However, due to the accuracy of this experiment and the theoretical analysis we have done, we can ensure This is this The first material that occurs“.
García-Vergniory believes: “PdGa crystals are very suitable for our demonstration: our calculations predict obvious observable effects, but very clean samples are necessary, and other materials are not available.”
These crystals were used in large-scale laboratories for experimental tests, in which the electronic structure was determined by synchrotron radiation through the light emission of electrons. Swiss Light Source (SLS) In Switzerland and Diamond light source in England.
This work is led by scientists Niels Schröter The Paul Scherrer Institute (PSI) in Switzerland, in addition to DIPC and synchrotron, also includes the Max Planck Institute for Physical Chemistry of Solids (Germany), the Swiss Federal Institute for Materials, Science and Technology (EMPA), and the Federal Institute of Technology in Lausanne College (EPFL), University of Oxford (UK) and University of Illinois at Urbana-Champaign (USA).
In the future, the research team intends to continue to study the influence of chirality on other crystal structures, and analyze its relevance in the catalytic process and its possible relevance to topological properties.
Ikerbasque researchers at DIPC, and co-authors of the study Maia Garcia Vergniory and Fernando de Juan. /DIPC
“Observation and Control of the Maximum Chern Number in Chiral Topological Semimetals”. NBM Schröter, S. Stolz, K. Manna, F. de Juan, MG Vergniory, JA Krieger, D. Pei, T. Schmitt, P. Dudin, TK Kim, C. Cacho, B. Bradlyn, H. Borrmann, M Schmidt , R. Widmer, VN Strocov, C. Felser. science 369, 179-183 (2020). DOI: 10.1126/science.aaz3480