(ORDO NEWS) — For the first time, American researchers managed to create a topological insulator (its surface layer conducts electric current) and observe quantum effects in it. This became possible thanks to the right material – bismuth bromide.
A topological insulator is a material that in volume is a dielectric (insulator), but its surface conducts electric current, that is, due to the internal topology, electrons can only move along the surface of the material. This unique property allowed scientists to demonstrate various quantum effects on topological insulators.
However, researchers from Princeton University (USA) were able to observe them for the first time at room temperature, while usually the observation of quantum states requires a temperature not much higher than absolute zero (minus 273.15 degrees Celsius).
In recent years, the study of topological states has been at the center of scientific interest of many researchers. This area combines quantum physics with topology, a branch of theoretical mathematics that studies the phenomenon of continuity.
New topological properties are in demand both from the point of view of fundamental physics and for the search for applications in quantum engineering and nanotechnologies.
The main problem is high temperatures, at which the surface electrons of the topological insulator invade inside: then the entire volume of the material also begins to conduct current, which weakens or destroys special quantum effects.
To overcome this limitation, it is possible to carry out experiments at very low temperatures, but this is laborious and impractical for many applications.
Now scientists have found a new way to get around this problem. Insulators, like semiconductors, have so-called band gaps – barriers that electrons cannot overcome. Sufficient band gap of the topological insulator allows to cope with the temperature increase.
But too large a band gap can disrupt the spin-orbit interaction of electrons – their interaction with their own magnetic moments. In this case, the topological quantum state is also destroyed.
Therefore, to maintain the quantum effect, it is necessary to find a balance between the band gap and the effect of spin-orbit interaction. Scientists managed to make such a topological insulator from bismuth bromide: the structure of this material made it possible to observe quantum effects even at room temperature.
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