In their investigation, the authors used a unique rotating cryostat. Credit: Mikko Raskinen/Aalto University
A group of researchers has demonstrated the energy dissipation in quantum turbulence, providing insights into turbulence on various scales, from microscopic to planetary.
Dr. Samuli Autti of Lancaster University worked with Aalto University researchers on a recent investigation into quantum wave turbulence.
The findings of the team, which have been published in Nature Physics, provide a new understanding of how wave-like motion alters the temperature at the microscales, and support a theoretical explanation for how the energy is dissipated at small scales.
"This discovery will become a cornerstone of the physics of large quantum systems," Dr. Autti said.
Quantum turbulence at large scales is difficult to simulate. At small scales, quantum turbulence is different from classical turbulence because the turbulent flow of a quantum fluid is restricted around line-like flow centres called vortices and can only take certain, quantized values.
This granularity makes quantum turbulence much more straightforward to capture in a theory, and it is generally believed that mastering quantum turbulence will help physicists understand classical turbulence as well.
A new quantum understanding of turbulence might allow for enhanced engineering in applications where fluids and gases, such as water and air, are a key issue in the future.
Dr. Jere Mäkinen, an Aalto University senior author, believes that her research with the basic turbulence building blocks might pave the way for further understanding of the interactions between various length scales in turbulence.
Understanding the properties of classical fluids will enable us to improve cars' aerodynamic performance, forecast weather with greater accuracy, or control water flow in pipes in a wide variety of scenarios.
Quantum turbulence, according to Dr. Autti, is a challenging problem for researchers.
“The formation of quantum turbulence around a single vortex has remained elusive for decades in experiments, despite an entire field of physicists studying quantum turbulence trying to find it. This includes people working on superfluids and quantum gases such as atomic Bose-Einstein Condensates (BEC). The theorized mechanism behind this process is called the Kelvin wave cascade.
"In the present paper, we demonstrate that this mechanism exists and works as predicted. This discovery will become a cornerstone of the physics or large quantum systems."
The Aalto Low Temperature Laboratory's senior scientist conducted a study of turbulence in the Helium-3 isotope in a rotating ultra-low temperature refrigerator. These researchers found that at microscopic scales so-called Kelvin waves act on individual vortices by continually pushing energy to smaller and smaller scales — ultimately determining the degree at which energy dissipation occurs.
"The issue of how energy disappears from quantized vortices at ultra-low temperatures has been crucial in the study of quantum turbulence," said Dr. Jere Mäkinen of Aalto University. In this experiment, the theoretical model of Kelvin waves transferring energy to the dissipative length scales is demonstrated for the first time in the real world."
The next challenge for the group is to manipulate a single quantized vortex by using nano-scale devices submerged in superfluids.
J. T. Mäkinen, S. Autti, P. J. Heikkinen, J. J. Hosio, V. S. L’vov, P. M. Walmsley, V. V. Zavjalov, and V. B. Eltsov, 2 March 2023, Nature Physics. DOI: 10.1038/s41567-023-01966-z J. T. Mäkinen, S. Autti, P. J. Heikkinen, J. J. Hosio, V. S. L'vov, P. M. Walmsley, V. V. Zavjalov, and V. B. Eltsov, 2 March 2023, Nature Physics. DOI: 10.1038/s41567-023-01966-z
