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Physics professor receives federal grant

Nikoleta Theodoropoulou

Physics professor receives federal grant

Sunday, October 1, 2023

Cutting-edge quantum research funded by U.S. Department of Defense

An $800,000 United States Department of Defense grant will be funding research conducted at Texas State University on the potential of exotic materials used for cutting-edge technologies. Associate Professor of Physics Nikoleta Theodoropoulou, PH.D., is studying the addition of transition metal oxides—perovskite oxides—to silicon and the electrical and magnetic properties that could create.

Theodoropoulou is a native of Greece, where she received her bachelor’s degree in physics, later coming to the United States to get her Ph.D. at the University of Florida.

She said her research will revolve around the quantum properties of transition metal oxides, and to simplify understanding of these concepts, it’s important to initially discuss quantum properties.

“It has to do with … how any random material behaves when it becomes very, very small or very, very cold,” Theodoropoulou said. “Quantum properties are properties that we use every day.” She added that we often don’t realize we are using quantum properties because it is happening on such a small scale—beyond our perceptual abilities.

Theodoropoulou noted that the results of her research will be applicable to technology and making it more efficient, faster and providing it with different functions. She said the research is of interest to the U.S. Department of Defense because quantum technologies is one of their main areas of focus. She said it can be useful in defense as it is applicable to devices used for communication and calculations.

Theodoropoulou said transition metal oxides are materials that contain some metals that, in addition to having charge, also have spin. According to the Science Learning Hub website, an electrical charge is created when electrons are transferred to or removed from an object. Because electrons have a negative charge, when they are added to an object, it becomes negatively charged. When electrons are removed from an object, it becomes positively charged. Scientific American describes spin as the total angular momentum, or intrinsic angular momentum, of a body, which gives a particle a tiny magnetic field called a magnetic moment.

“You can think of it as a magnet,” Theodoropoulou said. “It’s basically having two magnets interacting with each other … the magnetic behavior is actually spin.”

She said transition metal oxides are multifunctional because they have spin and charge and can interact with each other to create magnetic properties and electricity.

She added that the interaction of these materials can create different quantum properties such as ferroelectricity, multiferroicity and unconventional superconductivity.

She described ferroelectricity as a permanent source of electricity.

“You can think of ferroelectricity as something that always has a positive and negative charge far away from each other,” Theodoropoulou said. “It creates an electric field.”

She explained that multiferroicity as the primary goal of the research in which the properties would be both ferroelectric and ferromagnetic– containing both a permanent electric and a permanent magnetic field.

She went on to illustrate that superconductivity as a process of materials conducting electricity without having any resistance. She added that you can think of resistance in terms of a wire circuit; the circuit moves electricity from one point to another via an energetic cost, which creates heat.

“It’s not easy for electrons to go from one place to another,” Theodoropoulou said. “They feel this resistance, so they heat up.” She added that with superconductivity there is no resistance, so it is the free flow of charged particles going from one side of a wire to the other.

She said we use silicon in technology all of the time, which is beneficial because the charge can be manipulated, but it has drawbacks also; silicon has no multiferroicity, no ferroelectricity and no ferromagnetism as well as no net spin associated with the charges when used alone.

“But if we take silicon and we try to put—on top of it—in a very controlled manner, a layer of these transition metal oxides,” Theodoropoulou said. “What we effectively do is we couple or we add to silicon these nice properties.”

Theodoropoulou stressed that with this research, undergraduate and graduate Texas State University students will be getting trained on these cutting edge technologies: the growth of materials, how to process them and the physics behind it.

For those wishing to get a better understanding of the concept of spin, go to scientificamerican. com/article/what-exactly- is-the-spin/.

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