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[EN VIDÉO] What are the differences between an insulator and a conductor at the quantum level? Why are materials such as gold, silver or copper good electrical conductors? Its secret lies at the quantum level, mainly in the behavior of its electrons. Discover in video thanks to Everything Is Quantum the differences between an insulating material and a conductor. A material capable of memorizing the external stimulations it has undergone and adapting to them, just like our brain: it is hard to imagine that such a material exists, and yet vanadium dioxide (VO2) is the first representative! This semiconducting metal oxide was already known to have an insulator-to-metal transition, making it perfect for applications in the field of electronics, or even more surprising ones like intel windows clever! But researchers have discovered other surprising properties, described in a study published in Nature. Originally, vanadium dioxide has a sharp transition from insulator to conductor at 68 °C: a mixture between a Mott transition and a Peierls transition. When the temperature is lower than 68 °C, the electrons in VO2 are as if going to the atoms, due to the Coulomb repulsion between two atomic sites. But the energy provided by the heating of the material allows the electrons to leave their place and move in the VO 2. The Peierls transition, on the other hand, refers to the structure of the crystal lattice. The latter is distorted below the transition temperature, creating an energy gap between the conduction band and the valence band: the electrons are not free to move in the material. But when the temperature rises, the distortion disappears, allowing the electrons to escape from their atomic sites. That’s what Mohammad Samizadeh Nikoo, a PhD student at the Swiss Federal Institute of Technology in Lausanne (EPFL), did. Its initial purpose was to study its so-called “volatile” memory, that is, “the material returns to an insulating state right after the removal of the excitation”, specifies Samizadeh Nikoo in an EPFL press release , first author of the study. For this, he sent an electric current many times through a sample of vanadium oxide. “An electric pulse crosses the material and follows its way towards the exit”, specifies the scientist. Once the current has passed, cooling involves a return to the initial insulating state. The researcher wanted to know how long this return to the isolation state took. But it was there that he noticed another surprising effect: the vanadium dioxide behaved differently during the second electrical impulse, the time to return to the insulating state was not the same as in the first impulse, it was like if its structure had adapted to it. . “He remembers his last transition and anticipates the next one. This is an unexpected memory effect. This is not related to the electronic states, but to the physical structure of the material. This is a novelty from a scientific point of view, because no other material behaves like this”, says Elison Matioli, co-author of the study and director of the laboratory where the measurements were made. Currently, researchers have shown that this memory can last up to three hours. “If he remembers it so long later, it can be said that this memory can last for several days, but we currently do not have the necessary measurement tools to prove it,” continues E. Matioli. One thing is certain: this discovery opens up. it leads to many potential applications, in particular for memory-intensive computation operations. In fact, thanks to its strange behavior, vanadium dioxide is able to store more data (of different states) than conventional materials that are limited to binary information. In your case we are talking about structural memory, where the information is stored directly in the structural modifications you have made, while for the rest of the materials we are talking about electronic memory, where only two electronic states are possible.—LAST DAYS to take advantage of our summer offer. Subscribe to our media for a period of 3 months and receive Mag Futura as a gift!*Take advantage of the offer now *Offer valid for any new subscription from 3 months to offer “I participate in the life of Futura” on Patreon. — Are you interested in what you just read?
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