This could make today’s ultra-fast computers seem slow
Magnons, Bose-Einstein condensates and very bright people.
NTNU has many brilliant researchers, and some of them are working on new methods to transfer information more efficiently. Most of the time, they do this because they find it exciting, but a useful side effect is that their work can contribute to faster computers that consume little power.
One of them is Therese Frostad.
“I am working on spintronics, a research field that exploits electron spins to develop new technology,” says researcher Therese Frostad at NTNU’s Department of Physics.
If you didn’t understand the previous sentence, don’t despair, we will explain. First things first!
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Spin transmits the information instead of electrons
If you paid attention in your school science lessons, you might know that an electron is a charged particle in an atom. Electricity is basically just electrons moving along a material.
Therese Frostad. Photo: NTNU
In ordinary computers and other electronics, the information is transmitted using electricity, i.e. the electron current.
“However, heat generation is a problem because the speed of computers is increasing and the components are getting smaller and smaller – and closer and closer together,” says Frostad.
In other words, traditional technology is approaching a limit, and researchers are therefore looking for new ways to transfer information. One solution is to exploit the spin of electrons, which is what Frostad’s work involves. So what is this spin all about?
Electrons have spin
In addition to being charged, electrons have another characteristic called spin. Among other things, this is the starting point for magnetism.
Physicists like Frostad can manipulate this spin using magnetic fields so that the spin changes, and so that this change moves like a wave through the atoms of a material.
“In spintronics, we can use spin waves to carry information,” says Frostad.
These spin waves generate much less heat than electron currents do and may therefore offer a solution to the problem of heat generated by traditional electronics.
“Spintronics may also be able to help us develop technology that requires little energy,” says Frostad.
Erm… Bose-Einstein condensates?
During her doctoral work, Frostad worked with Bose-Einstein condensates, and they are a lot more exciting than you might think once you know what they actually are.
The strangest things happen in Bose-Einstein condensates – at least if you view them from a non-physicist perspective.
For example, a few years ago, a group of researchers managed to reduce the speed of light to just over 60 kilometres per hour in a Bose-Einstein condensate. In other words, a really good cyclist could beat the speed of light in a downhill race! This would be impossible under normal conditions, even if you trained really hard. But what exactly are these condensates?
Arne Brataas. Photo: NTNU
Most people know that a substance can be in a solid, liquid or gas state. In addition, there is plasma, which is a kind of gas with charged particles. And then there are Bose-Einstein condensates, although no one was really sure about their existence until just a few years ago.
The theory behind these condensates was the idea of Indian physicist Satyendra Nath Bose, who teamed up with super-celebrity Albert Einstein to publish the first article about them. This year will mark the centennial anniversary of the collaboration between these two physicists, but no one actually found a condensate in reality until 1995. Atomic condensates only occur at extremely low temperatures, close to absolute zero.
Physicists often like Bose-Einstein condensates because they are so well-suited for studying magnetic fields, gravity, and fundamental properties of substances.
You can also study spin waves in Bose-Einstein condensates, which is exactly what Frostad has been doing.
And magnons?
“Spin waves are called ‘magnons’,” Frostad explains.
At the same time, magnons are ‘bosons’, which are one of the two groups of particles that physicists talk about in quantum mechanics, and we now find ourselves all the way down at the nanolevel.
“When magnons accumulate in the lowest energy state, they can form a Bose-Einstein condensate. This is exciting, and we have recently begun to investigate whether we can use this magnon condensate to develop new technology,” says Frostad.
Perhaps the researchers can help develop quantum computers in which the magnon condensate is part of the technology?
Manipulated magnon condensates
“In order to be able to use the magnon condensate for something useful, we must first learn to control the properties of the condensate. This was the aim of the research in my doctoral thesis,” says Frostad.
Alireza Qaiumzadeh. Photo: NTNU
During her work, Frostad made theoretical calculations related to how we can make magnons, and how the condensate’s magnons interact with and influence each other.
“We investigated how to control the properties of the condensate using external magnetic fields, and how to change the properties of the materials and systems in which we made the condensate,” says Frostad.
Multiple areas of application
Frostad’s academic supervisor was Professor Arne Brataas at NTNU’s Department of Physics.
“The research expands the possibility of controlling Bose-Einstein condensates and may be used in future quantum-sensor technology,” says Professor Brataas.
He is supported by Frostad’s collaborator, researcher Alireza Qaiumzadeh at the Department of Physics.
“One of the advantages of magnon condensates is that they can exist at room temperature. In the future, magnon Bose-Einstein condensates may be used as sensitive detectors in fundamental science,” says Qaiumzadeh.
Fundamental science will enable us to understand more about the basic mechanisms behind different natural phenomena. Qaiumzadeh points out that no one knew what to use lasers for when they were first invented either. You never know what might come in useful.
“We have an idea that this could be used to detect axion dark matter,” says Qaiumzadeh.
No, I don’t know what that means either, but I do know that it is about fundamental physics and how the world around us works, and that much is really fascinating.
References:
Frostad, T., Skarsvaag, H. L., Qaiumzadeh, A., & Brataas, A. (2022). Spin-transfer-assisted parametric pumping of magnons in yttrium iron garnet. Physical Review B, 106(2), 024423. Kristoffersen, A.-L. https://journals.aps.org/prb/abstract/10.1103/PhysRevB.106.024423
Frostad, T., Pirro, P., Serga, A. A., Hillebrands, B., Brataas, A., & Qaiumzadeh, A. (2023). Anisotropy-assisted magnon condensation in ferromagnetic thin films. ADS. https://ui.adsabs.harvard.edu/abs/2024PhRvR…6a2011F/abstract
