Physicists Have Created A Two-Dimensional Quantum Spin Liquid
Japanese researchers have found out that a synthetic analog of a mineral found in Kamchatka contains a new exotic form of matter, a two-dimensional quantum spin liquid. A description of the scientists' work is available in the scientific journal Nature Communications.
"The creation of quantum spin liquids has become one of the most important achievements both for the study of condensed matter physics and for the creation of spintronic electronic devices. We have never observed its two-dimensional form before, which was due to discrepancies between theory and practice," said one of the authors of the study, associate Professor Masayoshi Fujihala of the Tokyo University of science.
So-called quantum spin liquids are an exotic form of matter that consists of a specific set of atoms or ions, the electron spins of which behave chaotically even at very low temperatures, like water and other liquid molecules.
Scientists predicted their existence more than forty years ago, but the first analogs of quantum spin liquids were discovered by physicists from China and the United States only in 2016. The creation of this form of matter was a particularly important event for the world of physics because it was one of the first to experimentally confirm that the so-called Majorana fermions – particles that are their antipode-can exist in reality.
Fujihara and his colleagues have created an even more exotic two-dimensional form of the matter. They experimented with substances that are similar in structure to a mosaic of triangles and squares and yet have antiferromagnetic properties.
Quantum atomic mosaic
This is what researchers call a special class of materials in which the magnetic moments of atoms are not directed in one direction, as in ordinary magnets, but are stacked in "staggered" order. As a result, they neutralize each other and do not create an external magnetic field. Thanks to this "packing" of atoms, antiferromagnetic materials can be used for a super-dense recording of information.
Theoretical physicists have long assumed that antiferromagnetic materials, whose structure is similar to a mosaic of alternating triangles and squares, will have an unusual set of properties, thanks to which they can form thin layers of one atom thick with the properties of a quantum spin liquid.
Scientists from Japan and Australia drew the attention of that natural mineral Atlasova very similar structure. This mineral was discovered by Soviet geologists in 1987 in the vicinity of the Tolbachik volcano in Kamchatka. It is a complex compound of sulfuric acid, oxygen, chlorine, iron, bismuth, potassium, and copper.
Masayoshi Fujihala and his colleagues found that replacing iron with aluminum in a special way changes the structure of this substance and causes the electrons in certain layers of it to behave chaotically even at ultra-low temperatures-just as their counterparts do in three-dimensional versions of a quantum spin liquid.
Interestingly, the results of observations of the behavior of electron spins at different temperatures did not coincide with what is predicted by the standard theoretical model, which describes the structure of such atomic "mosaics," their magnetic properties and the mechanism of the birth of a quantum spin liquid in them.
Why this is so, scientists do not yet know. However, they suggest that existing theoretical calculations do not take into account how the behavior of particles in this liquid is affected by their interactions with atoms and electrons, which are located at a great distance from them. The researchers hope that further experiments will help them formulate a new theory that will allow them to predict the properties of such two-dimensional quantum liquids and use them in practice.