Scientists have been using topological insulators to demonstrate quantum effects for more than a decade, but...
Quantum physics and topology - together
In recent years, the study of topologicalstates of matter has attracted the attention of physicists and engineers around the world. This field of study combines quantum physics with topology, a branch of theoretical mathematics that studies geometric properties that can be deformed but not essentially changed. The topological properties of matter are important both from the point of view of fundamental physics and for applications in quantum engineering and next-generation nanotechnology.
Basis of quantum topology
The main component of the device used forresearch into the mysteries of quantum topology - topological insulator. The unique device acts as an insulator on the inside, meaning the electrons inside cannot move freely and therefore do not conduct electricity.
But electrons at the edges of the device are free tomove, and therefore are conductive. Thanks to the special properties of the topology, electrons flowing along the edges are not interfered with by any defects or deformations. The new device could not only improve future technologies, but also provide a deeper understanding of matter itself by exploring its quantum electronic properties.
What is the problem?
Still using materials and devicesfor real applications in functional devices was problematic. All due to the harsh conditions of quantum topology. Yes, there is now a huge interest in topological materials, and people often talk about their great potential for practical applications. But until some macroscopic quantum topological effect manifests itself at room temperature, this will all remain just a dream.
The problem is that the environment or hightemperatures create what physicists call “thermal noise.” In simple words, this is an increase in temperature at which atoms begin to vibrate strongly. This can disrupt the operation of subtle quantum systems, thereby destroying the quantum state itself.
In particular, in topological insulators thesehigher temperatures create a situation in which electrons on the surface of the insulator intrude into the interior of the insulator. This causes the electrons to conduct current, which weakens or destroys the special quantum effect.
Is there a way around this?
Yes, by conducting such experiments under conditionsexceptionally low temperatures - at absolute zero or so. At these incredibly low temperatures, atomic and subatomic particles stop vibrating and are therefore easier to manipulate. However, creating and maintaining an ultra-cold environment is impractical for many applications; it is expensive, cumbersome and requires a huge amount of energy.
What have the scientists done?
Physicists have developed an innovative way to circumventproblem. They created a new type of topological insulator from bismuth bromide (chemical formula α-Bi 4 Br 4). It is an inorganic crystalline compound that is sometimes used for water purification and chemical testing. As the authors of the study note, the material does not require enormous pressure or an ultra-high magnetic field.
In their study, the scientists relied onThe quantum Hall effect is a form of topological effect that was discovered by Klaus von Klitzing in 1980, for which he received the Nobel Prize five years later. Since then, topological phases have been intensively studied. Scientists have discovered many new classes of quantum materials with topological electronic structures, including topological insulators, topological superconductors, topological magnets, and Weyl semimetals. Their electronic spectrum is a three-dimensional analogue of the spectrum of graphene.
The last piece of the puzzle
To achieve quantization at room temperature, the scientists used the kagome lattice.
The term kagome lattice was coined by a Japanese physicist.It first appeared in a 1951 article written by Ishiro Shoji under the direction of Fushimi. The kagomes lattice consists of the vertices and edges of a trihexagonal mosaic. Contrary to the name, these intersections do not form a mathematical lattice. In turn, a trihexagonal mosaic is one of the 11 homogeneous mosaics on the Euclidean plane made of regular polygons. The mosaic consists of regular triangles and regular hexagons, arranged so that each hexagon is surrounded by triangles, and vice versa. The mosaic's name comes from the fact that it combines a regular hexagonal mosaic and a regular triangular mosaic.
Topological insulators on a kagome latticecan be designed to have relativistic band crossings and strong electron-electron interactions. Both are necessary for a new type of magnetism.
Lattice kagome. Author: N.Mori
So scientists realized that kagome magnets area promising system for searching for topological magnetic phases. They themselves are similar to topological insulators - it's all a matter of suitable atomic chemistry and structural design.
Where it leads?
The researchers believe that their breakthrough will lead to the development of quantum and nanotechnology.
The creation of a new insulator will have a particular impactfor the development of next generation quantum technologies. The researchers also believe that the breakthrough will accelerate the development of more efficient and “green” quantum materials.
What's next?
According to scientists, now the theoretical and experimental focus of the research team is concentrated in two directions.
First, scientists want to understand what othertopological materials can operate at room temperature. And, importantly, provide other experts with tools and new measurement techniques to identify materials that will perform at room and high temperatures.
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