Normally, when something warms up, the heat tends to spread outward before eventually dissipating. However, in the world of superfluid quantum gases, things are a little different.
For the first time, scientists at the Massachusetts Institute of Technology have successfully visualized how heat actually travels through this exotic fluid in waves known as “second sound.”
Understanding this dynamics can help answer questions about high-temperature superconductors and neutron stars.
In the average everyday material world, heat tends to spread from local sources. If you drop burning coal into a pot of water, liquid The temperature slowly increases before the heat is finally dissipated. However, the world is full of rare and exotic materials that are not like that. that’s right Follow these laws of heat.
These superfluid quantum gases “flop” their heat from side to side, rather than spreading out as expected. So it essentially propagates heat. wave. Scientists call this behavior the “second sound” of matter (the first is the normal sound caused by density waves). This phenomenon has been observed before, but never imaged. But recently, scientists at the Massachusetts Institute of Technology (MIT) were finally able to capture this movement of pure heat by developing a new method of thermography (also known as heat mapping).
The study results were published last week in a diary science,and, university press release Highlighting this achievement, MIT assistant professor and co-author Richard Fletcher continued with a boiling pot analogy to explain the inherent strangeness of “seconds.” sound”These exotic superfluids.
“It’s like having a tank.” water Half of it was on the verge of boiling over,” Fletcher said. “Then you look and the water itself may seem perfectly calm, but then all of a sudden it gets hot on the other side, and then the other side gets hot, and the heat goes back and forth, while the water stays perfectly still. It looks like it is.”
These superfluids are created when clouds of atoms are exposed to near-extreme temperatures. absolute temperature (-459.67°F). In this rare state, atoms behave differently because they create an essentially frictionless fluid. In this frictionless state, heat is theorized to propagate like waves.
“Second tones are a characteristic of superfluidity, but so far in cryogenic gases we have only been able to see them in faint reflections of density.” ripples That goes along with it,” lead author Martin Zwierlein said in a press statement. “The nature of heat waves has never been proven.”
To actually capture this second sound, Zweerlein and his team had to think beyond the usual thermal box. Tracing the heat of ultra-cold objects is a big problem because they don’t emit normal infrared radiation. So MIT scientists have designed a way to harness radio frequencies to track a particular subatomic particle known as a “lithium-6 fermion.” These particles can be captured in a variety of ways. frequency Relationship with temperature (i.e. higher temperature means higher frequency and vice versa). This new technique essentially allowed the researchers to focus on “hotter” frequencies (which are still very cold) and track the resulting second wave over time.
This may feel like a big “so what?”After all, when was the last time you had a close encounter with a superfluid? quantum gas? But ask a materials scientist or astronomer and you’ll get a completely different answer.
Exotic superfluids may not fill our lives (yet), but understanding the properties of second-wave motion could help answer questions about high temperatures. superconductor (Again, not yet very low temperatures), or the messy physics at the heart of it. neutron star.
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