Space and Physics
PUBLISHED
Particles can be divided into two broad categories: one called bosons and the other called fermions. Bosons love to be near each other, and many of them can share the same quantum state. Fermions, on the other hand, can never share the same quantum state.
New research has now shown that it's possible to make these groups of particles form a stable, self-bound quantum droplet.
It’s not that fermions and bosons don't interact, but usually these interactions tend to be weak. This is especially true at ultracold temperatures where the bosons enter the fifth state of matter, becoming a Bose-Einstein condensate.
The formation of a droplet with both types of particles was not thought likely to exist.
This new work instead shows that the right circumstances can actually be created to mix the two. The quantum droplets form due to an attractive force between them, and at the same time, the cantankerous fermions produce a push that keeps the droplet from collapsing.
"Previous theories could only describe these systems when the particles interacted relatively weakly," said lead author Sam Foster, a graduate researcher at Monash University, in a statement. "Our new approach lets us explore what happens when those interactions become much stronger, which is where the most interesting physics emerges."
The theory suggests that the formation of these droplets would be a phase transition similar to the change from a liquid to a gas. These quantum phases are not governed by the rules that we are familiar with in the classical physics world.
"Quantum systems can behave in ways that seem impossible in our everyday world," added Foster. "We've shown that these two very different types of particles can balance each other perfectly to create a stable droplet that effectively holds itself together."
The team believes that theoretical predictions can be tested with the current experimental setup, without the need for new fancy methods. Being able to create the droplets and to study their actual properties could unveil new insights into quantum materials that could be applied to future technologies such as quantum computing and quantum sensors.
"Understanding how matter organises itself under extreme quantum conditions gives us new tools for designing and controlling quantum systems," Foster continued. "While this is fundamental research, discoveries like this often become the foundation for tomorrow's quantum technologies."
A paper describing the results was published in the journal Physical Review Letters.
