A new “unexpected” phenomenon discovered in quantum physics

Researchers at Northeastern University have discovered a new quantum phenomenon in a particular class of materials called antiferromagnetic insulators. This has the potential to create new ways to power “spintronics” and other future technology devices.

This discovery is “how heat flows in a magnetic insulator, [and] how [researchers] You can detect that heat flow. ” Gregory FieteProfessor of Physics

Gregory Fiete, Professor of Physics at Northeastern University. Photo courtesy of Matthew Modoono / Northeastern University

Co-author of the study in Northeastern.New effects published in Nature Physics This week, experimentally demonstrated, lanthanum ferrite (LaFeO3) was observed in combination with a layer of platinum or tungsten.

“That layered bond is the cause of the phenomenon,” he says. Arun BansilHe is a prominent professor at the University of Northeastern University School of Physics and participated in this study.

According to Bansil, this discovery has many potential uses, including improved thermal sensors, waste heat recycling, and other thermoelectric technologies. This phenomenon can even lead to the development of new power supplies for these, and other emerging technologies.Northeastern graduates Students Matt Mazzell and Bernardo Barbielini, computational and theoretical physicists at the Lappeenranta Institute of Technology, who are currently visiting the northeast, participated in the study.

To explain the team’s findings, we need a significant (literally) magnification to observe the world of atomic-scale particles, especially the nanolife of electrons. You also need to understand some properties of electrons. Electrons have what is called a “spin”, which has an electric charge and can generate a heat flow as it travels through the material.

Electron spin, or angular momentum, represents the basic properties of an electron defined by one of two potential states: up or down. There are various ways in which these “upward or downward” spins of electrons (think of them as the North and South Pole) can orient in space. This produces different types of magnetism. According to Bansil, it all depends on how the atoms are patterned on a particular material.

In magnetic systems, the spins of the material are usually aligned in the same direction. Its electron configuration in a magnetic (or “ferromagnetic”) crystal creates a force that attracts and repels other crystals. Many magnetic materials also conduct electricity when electrons can flow through them. These materials are called conductors because they can conduct electricity.

Arun Bansil, a prominent professor of university physics. Photo courtesy of Matthew Modoono / Northeastern University

In addition to generating an electric current, the movement of electrons through the material also carries the thermal current. When an external electromagnetic field is applied to a material that conducts electricity, a thermal current is generated.

“Heat is when these electrons sway fast or slow, so they can carry more or less heat energy,” says Bansil.

Normally, the spin current flows in the same direction as the heat current, says Bansil. However, with the particular material used in this study, “it flows perpendicular to the direction of the heat flow.”

“That’s the new thing here,” says Bansil.

This “unexpected” interaction opens the door to new ways of thinking about power generation.

“What we want to do is create a magnetic stream that produces electricity. The way we do that is to generate voltage,” says Fiete.

To that end, researchers have combined antiferromagnetic insulating materials (here LaFeO3) with other heavy elements such as the conductors platinum and tungsten. The coupling throws electrons slightly into the off-quilter.

“This particular material has spins that are almost completely reverse-oriented on the closest adjacent atom,” says Fiete. Inclined.. They are not completely anti-directional — they are mostly, but with a slight twist. And that small offset is actually very important. Because it’s part of what produces the interesting effects you’ll see in your project. “

Here’s what this particular class of material is named for. It is an inclined antiferromagnetic material.

A new class of electronic devices, so-called “spintronics,” rely on the manipulation of electron spins to improve the information processing capabilities of future technologies. Another related discipline, called spin caloritronics, focuses on “how to convert heat flow into magnetic flow, or spin current, and finally to voltage.”

“Quantum physics of materials is particularly interesting because it is directly related to many technologies such as quantum computing, quantum sensing, and quantum communication,” says Fiete. “And what’s really getting a lot of attention … for now is how to move research from universities like the ones my team is involved to to technologies that affect our lives. . “

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