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Physics: an exotic magnetic state of matter discovered

Physics: an exotic magnetic state of matter discovered

A team of scientists from the United States has discovered a magnetic state of matter, found for years and referred to as an “antiferromagnetic excitonic insulator“. More generally this is a new type of magnet and because magnetic materials are at the heart of much of the technology around them, the new types of magnets are truly fascinating and promising for future applications.

This new magnetic state involves a strong attraction between electrons in a layered material which allows the electrons themselves to organize their magnetic moments in a normal “antiferromagnetic” pattern. This idea was first envisaged in the 60s when physicists explored the different properties of metals, semiconductors and insulators.

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Physics, a new state of matter discovered

In those years, physics was still trying to understand how the rules of mechanics apply to the electronic properties of materials. They were trying to figure out what happens while shrinking the electronic energy gap between an insulator and a conductor. However, is it just that or is it something else? The prediction was that under certain conditions, something more interesting could happen, namely the‘”Exciton antiferromagnetic insulator”, discovered now in the new study. However, why is this material so interesting? To understand this we need to get better inside how a new state of matter is formed.

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In an antiferromagnet, the electrons on adjacent atoms have their own magnetic polarization axes aligned in alternating directions. As far as the whole materials are concerned, these magnetic orientations cancel each other out, resulting in no net magnetism within the material. These materials can be replaced very quickly between different states. They are also quite resistant to information loss due to interference from external magnetic fields. These specific properties are very attractive as well interesting for modern communication technologies. Then the researchers dealt with the excitonic; Excitons occur when certain conditions allow electrons to move and interact with each other to form bonded states.

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Energy between electron-hole interactions

In the case of electron-electron interactions, the bond is driven by magnetic attractions strong enough to overcome the repulsive force between the two similarly charged particles. In the case of electron-hole interactions, the attraction must be strong enough to overcome the “energy gap”Of the material, a characteristic of an insulator. The latter is the opposite of a metal; is a material that does not conduct electricity. To make electrons move, they need an energy boost large enough to bridge a characteristic gap between the ground state and a higher energy level.

Under very special circumstances the energy gain between electron-hole magnetic interactions can exceed the energy cost of electrons jumping the energy gap. Now, thanks to advanced techniques, physicists they can explore those special circumstances to learn how the antiferromagnetic excitonic insulator state emerges. The identification of the antiferromagnetic excitonic insulator completes a long journey by exploring the fascinating ways in which electrons choose to organize themselves in materials. In the future, understanding the connections between spin and charge in such materials could have the potential for implementation of new technologies.

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Image by MasterTux from Pixabay