Atoms have come closer together than ever before, and seemingly impossible quantum effects have emerged.
Scientists have compressed two layers of ultracold magnetic atoms to a distance of 50 nanometers, ten times closer than in previous experiments, revealing unprecedented strange quantum effects.
The extraordinary proximity of the atoms will allow researchers to study quantum interactions at this length scale for the first time and could lead to significant advances in the development of superconductors and quantum computers.
This finding is reported in a new study published May 2 in the journal Science.
Extraordinary Quantum Behavior
Li Du, a physicist at MIT and the lead author of the study, said, “In the nanokelvin regime, there is a type of matter called Bose-Einstein condensation, where all particles behave like waves. These particles are essentially quantum mechanical objects.”
The interactions between these isolated systems are particularly important for understanding quantum phenomena such as superconductivity and superradiance. However, the strength of these interactions typically depends on the separation distance, which poses practical challenges for researchers studying these effects.
Overcoming Experimental Limitations
“In most cold atom experiments, there are limitations because the atoms used need to be in contact to interact,” Du said. “We are interested in dysprosium atoms because these atoms can interact with each other through long-range dipole-dipole interactions. However, even these long-range interactions cannot achieve certain quantum phenomena because the dipole interaction is too weak.”
Zooming atoms with optical tweezers
The research team found a way to overcome this limitation by using another quantum property of dysprosium atoms: their spins. Atomic spins can point either up or down, which means they have slightly different energies. The team used two different laser beams with slightly different frequencies and polarization angles to trap spin-up and spin-down dysprosium atoms separately.
BCS Coupling and Superconductivity
After building this bilayer system, the team launched a series of experiments to study quantum interactions at close range.
The team literally heated one of the two dysprosium layers separated by a vacuum gap and observed heat transfer in the empty space.
“Typically, heat transfer requires contact or radiation, which is absent here,” Du said. “But we still see heat transfer, and this is necessarily due to long-range dipole-dipole interactions.”
This remarkable heat transfer is just one of the strange effects the team has been studying. The team has also begun to study how this bilayer interacts with light. But Du is particularly interested in another quantum effect called Bardeen-Cooper-Schrieffer (BCS) coupling. BCS coupling is a quantum-bound state that some subatomic particles experience at low temperatures and is crucial for superconductivity.
Future Work and Progress
“BCS coupling is very important for superconductivity,” Du said. “A few years ago, there was a theoretical paper predicting that this kind of bilayer system could form BCS coupling when bound by long-range dipole-dipole interactions. We have not been able to see this experimentally before, but now it might be possible with our system.”
