Ah, quantum mechanics: endlessly interesting, and even though we’ve been working on the subject for about a hundred years, it’s still largely a collection of puzzles and questions. One of those issues was the question of what it actually feels like to put your hand in a superfluid. During a pilot study, scientists “accidentally” discovered what it feels like to touch superfluid helium-3.
Samuli Autti is the scientist who made this discovery. His research has been published in the journal Nature Communications. “We originally planned to investigate something completely different,” Otte says. Scientias.nl. “The original plan was to see what happens when you hit a superfluid very hard with a rod. Traditionally, quantum mechanics thought the superfluid should respond to this. However, what we saw was that the helium-3 superfluid remained completely negative no matter how hard we tried.”
What is superfluid?
To properly explain a superfluid, we must first look at what a “normal” fluid is. Let’s look at a glass of water as an example. At the molecular level, water molecules are attracted to each other enough that individual molecules cannot easily escape. At the same time, there is enough space for each molecule to do its job individually. Some water molecules go to the left, some to the right, and some collide with each other. In the case of superfluids this is not the case. In a superfluid, molecules “know” each other where other molecules are, and behave more as a whole. This is also called the “system”.
One special property of liquid helium-3 is that it behaves very differently from a “conventional” liquid when you make it very cold. For example, the experiment was performed at a temperature of a thousandth of a degree Kelvin above absolute zero. At this temperature, helium-3 turns into a superfluid, with its molecules behaving more like waves than “conventional” particles. For example, in a superfluid, all the molecules are moving in the same direction at the same time, rather than all going their own way more or less. This modified behavior makes it possible for these superfluids to move completely without friction.
“So, as we found in our previous experiment, it is not possible to break the quantum state of a superfluid. This means that you will not experience any pressure when you put your hand in it. “It is as if your hand is in a vacuum,” Otte explains. “Just like a vacuum, no Super liquid helium-3 can conduct heat.”
However, this is not the whole story. Because although the research did not go as expected, Otte made another discovery that came as a complete surprise. “What we learned during the experiment is that there appears to be a very thin layer along the edges of the superfluid.” So the researchers concluded that the helium-3 superfluid was, as it were, packed into a subsystem: a very thin layer of helium-3 that reacted differently from the rest of the superfluid and could therefore conduct heat.
“Imagine there is a ‘warm’ surface in superfluid helium-3. You feel hot the moment you touch it. But the moment you don’t touch it, you don’t feel anything at all,” Otte explains. This “warm” surface refers to the very thin layer surrounding helium-3. “Since touching an object requires sensing pressure and temperature, we can now say what it feels like to touch helium-3.” Otte describes the whole experiment as follows: “It will be a two-dimensional superfluid. The bulk of the helium-3 would appear empty, like a vacuum, while heat in a 2D subsystem would extend along the edges of the superfluid, and thus also along your finger.
Although touching superfluid helium-3 is not an everyday occurrence for most people, the result of the study is still very valuable. For example, helium-3 is one of the most versatile macroscopic quantum systems used in laboratories. Features of superfluids in studies of the Higgs mechanism, the Keppel mechanism, and quantum information processing research. “This research redefines our understanding of superfluid helium-3,” Otte said. “This could have far-reaching consequences for science.”
A complete understanding of quantum mechanics is not currently possible, even for scientists. In order to explain quantum mechanics in a fairly understandable way, the sciences In the past I spoke with Professor Ton van Leeuwen. He basically describes quantum mechanics as a set of equations that we use to describe reality. It is the best model we have for this purpose, but the consequences of this model are often counterintuitive. Central to this, among others, is the idea that particles can behave not only as particles, but also as waves. We see this behavior, among others, in superfluids, where all the molecules are moving in the same direction at the same time. Would you like to learn more about quantum mechanics? Read the interview with Van Leeuwen here.