Researchers found an unusual topology of sodium chloride

A research team found the unusual topology of sodium chloride (commonly known as table salt), which is not only helpful to understand the mechanism behind the dissolution and formation of salt, but also may pave the way for the design of nano conductive quantum wires in the future.

The joint research team of the Hong Kong University of Science and Technology and the University of Tokyo found an unusual topology of sodium chloride (commonly known as table salt), which is not only helpful to understand the mechanism of salt dissolution and formation, but also may pave the way for the future design of nanoscale conductive quantum wires.

In our daily life, there are all kinds of advanced materials, and many small tools and technologies are assembled from different materials. For example, mobile phones use a combination of different materials - glass as the display, aluminum alloy as the frame, and gold, silver, copper and other metals as the internal wiring. But nature has its own way of genius, "cooking" different properties into a magical material, or "topological material".

Topology, as a mathematical concept, studies which aspects of the object are robust under smooth deformation. For example, we can squeeze, stretch or twist a t-shirt, but as long as we don't tear it apart, its number of openings is still four. The discovery of the topological phase of matter emphasized by the 2016 Nobel Prize in Physics shows that some quantum materials are essentially a combination of electrical insulators and conductors. This may require a conductive boundary, even when the body of the material is insulated. This material is neither classified as a metal nor an insulator, but a natural combination of the two.

Although the topological properties of materials attract many research interests, they are only realized in a group of unique exotic materials, such as two-dimensional graphene. However, in a recent study, Professor Bao Haichun, an assistant professor of the Department of Physics at the Hong Kong University of Science and Technology, and his collaborator Professor Haruki Watanabe of the University of Tokyo found an amazing connection between topology and a large number of common substances, including salt.

Salt or sodium chloride is one of the most common crystals

, which often appears as a typical ionic compound in high school chemistry textbooks. For a long time, people thought that this well-known substance was tedious in topological structure. However, the research team found that, in theory, salt can actually achieve a recently introduced "high-order" topology. The zero dimensional angle of a salt is not a two-dimensional surface or a one-dimensional edge, but shows an abnormal behavior, in which the charge is effectively decomposed into one eighth of the basic unit of nature. In addition, the robustness of this topological property means that the results will be maintained even if the chemical structure is modified to other forms, such as silver chloride or potassium fluoride.

Professor Watanabe said that the connection between topological materials and everyday substances such as salt was completely unexpected. Professor Po said that this result shows that there is a neglected aspect of the topological structure of common ionic compounds. "This discovery may inspire the future design of nanoscale conductive quantum wires or new drug delivery methods, which are often studied together with the salt dissolution process," said Professor Po, adding, "It's interesting to realize how we take some electrons in every meal."

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