A charge sensor is used to measure the cost of electrons surfing on the spin wave.
A change in electron spin could change how devices store and carry information. These waves don't scatter or couple with other particles. They can act like a superfluid, moving through a material with zero energy loss.
The very properties that make them so powerful make it nearly impossible to measure. Researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences were able to detect spin waves in a two-dimensional graphene magnet, but they couldn't measure their specific properties.
Researchers from the SEAS have demonstrated a new way to measure the spin waves in Graphene.
In previous experiments, we only knew that we could generate spin waves, but we didn't know anything about their properties in a quantitative way. The energy and number of spin waves, their chemical potential, and temperature can be determined with this new work. We can use this tool to explore new ways of generating magnons and get closer to achieving spin superfluidity.
The research is published in a journal.
The properties of a spin wave are similar to the properties of a tidal wave. How could you measure the speed, height, or number of waves if you couldn't see the water? One way is to introduce something that you can measure, like a surfer. The surfer's speed could be used to detect the wave's speed.
Yacoby and his team used an electron surfer.
The researchers used a quantum Hall ferromagnet. The electron spins of the magnets are the same direction. If an electron with a different spin is introduced into the system, it will use energy to flip its neighbors.
The research team found that when they injected an electron with a different spin into the system, the energy it needed to flip its neighbors went down.
Andrew T. Pierce, a graduate student at SEAS and co-first author of the study, said that the electrons that are put into the system are sensitive to the presence of spin waves. It's almost as if these electrons are grabbing onto the wave and using it to flip their neighbors' spins.
"Spin waves don't like to interact with anything but by using electrons and this energy cost as a proxy to probe the properties of a spin waves, we can determine the chemical potential, which combined with knowing the temperature and a few other properties, gives us a full description of the mag This is important to know if the wave is reaching the limit.
The research could provide a general approach to studying other hard-to-measure exotic systems, such as the recently discovered moiré materials which are expected to support a variety of waves like the spin wave studied in this work.
The research was co-authored by several people.
Andrew T. Pierce and his team studied the dynamics of free and bound magnons in graphene. There is a DOI: 10.1038/s41567-021-01421-x.
Nature physics journal information.
The new method to measure spin waves brings us one step closer to superfluidity.
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