C'est la première fois qu'une capacité d'apprentissage est observée chez un matériau. © Olga, Adobe Stock

Scientists have never had such a learning-capable material!

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[EN VIDÉO] What are the differences between an insulator and a conductor at the quantum level?
Why are materials like gold, silver or copper good conductors of electricity? Their secret lies at the quantum level, mainly in the behavior of their electrons. Discover the differences between an insulating material and a conducting material in the video thanks to Everything Is Quantum.

A material that can be remembered stimulation external conditions to which it has been exposed and to adapt to them, just like our brain function
The brain is located in the cranial box and is the seat of higher (cognitive functions, senses, nerve reactions) and vegetative functions. It is therefore an essential organ that regulates everything…” data-image=”https://cdn.futura-sciences.com/buildsv6/images/midioriginal/5/c/b/5cb474dd85_121782_cerveau-3d .jpg” data – url=”https://news.google.com/health/definitions/biology-brain-3125/” data-more=”Read more”>Brain : hard to imagine that this type of material exists, and yet vanadium dioxide (VO2) is the very first representative! This semiconducting metal oxide was already known to have an insulator-to-metal transition, making it perfect for electronic applications, or even other more amazing ones, such as electronics smart windows ! But researchers have discovered other surprising properties, described in a study published in Nature.

Originally, at 68 °C, vanadium dioxide has an abrupt transition from insulator to conductor: a mixture between a Mott transition and a Peierl’s transition. If the temperature is below 68°C, the electrons of the VO2 are like “attached”. atoms, due to the Coulomb repulsion between two atomic sites. But’energy by heating the material causes the electrons to leave their place and move in the VO2.

The Peierls transition, on the other hand, affects the structure of the crystal lattice. The latter is distorted below the critical temperature, creating a gap. Between the two bands there is an energy gap where no carrier can find itself, that’s a band…” data -image=”https://cdn.futura -sciences.com/buildsv6/images/midioriginal/3/ c/b/3cb260fb3d_50034871_img366.jpg” data-url=”https://news.google.com/sciences/definitions /physics-gap-5120/” data-more=”Read more”>gap energy between conduction band and the valence band : The electrons cannot move freely in the material. But as the temperature increases, the distortion disappears, allowing the electrons to leave their atomic places.

An accidental discovery

Surprising for that insulator-metal transition, vanadium dioxide is the subject of numerous studies to determine in which areas it could be used. Mohammad Samizadeh Nikoo, a doctoral student at the Swiss Federal Institute of Technology in Lausanne (EPFL), did just that. His original goal was to study his so-called “ephemeral” memory, that is “the material returns to the insulating state immediately after the excitation is removed”specifies Samizadeh Nikoo in a EPFL press release, first author of the study. For this he sent in many times Electrical power in a vanadium oxide sample. “An electrical impulse penetrates the material and continues on its way to the exit”says the scientist.

The pulse makes it possible to heat the material and thus perform the expected insulator-to-metal transition. Once current flows, cooling involves a return to the initial insulating state. The researcher wanted to know how long this return to the isolating state took. But there he noticed another amazing effect: The vanadium dioxide behaved differently in the second electrical impulsethe time to return to the isolator state was not the same as for the first pulse.

It was as if its structure had adapted to it. “He remembers his last move and awaits the next one. This is an unexpected memory effect. This is not related to electronic states, but to the physical structure of the material. From a scientific point of view, it is a first because no other material behaves like this.”, says Elison Matioli, co-author of the study and head of the laboratory where the measurements were taken. Currently, researchers have shown that this is the case memory can take up to three hours. “If he remembers it that long afterwards, it’s fair to say that that memory can last for several days, but we don’t currently have the necessary measuring tools to prove that.”continues E. Matioli.

One thing is certain: this discovery opens the Goal too many applications potential, especially for arithmetic operations that require memory. In fact, thanks to its strange behavior, vanadium dioxide is able to store more data (in different states) than traditional information-limited materials binaries. With it one speaks of structural memory, in which the information is stored directly in the structural modifications made by it, with other materials one speaks of electronic memory, in which only two electronic states are possible.

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