Strength in numbers: Physicists identify new quantum state allowing three -- but not two -- atoms to stick together

( -- A Kansas State University-led quantum mechanics study has discovered a new bound state in atoms that may help scientists better understand matter and its composition.

The yet-unnamed bound state, which the simply refer to as "our state" in their study, applies to three identical loosely bound together -- a behavior called three-body bound states in . In this state, three atoms can stick together in a group but two cannot. Additionally, in some cases, the three atoms can stick together even when any two are trying to repel each other and break the connection.

"It's really counterintuitive because not only is the pair interaction too weak to bind two atoms together, it's also actively trying to push the atoms apart, which is clearly not the goal when you want things to stick together," said Brett Esry, university distinguished professor of physics at Kansas State University and the study's lead investigator.

Esry, along with Kansas State University Nicolais Guevara and University of Colorado-Boulder colleague Yujun Wang -- a Kansas State University graduate -- calculated the quantum state in their study, "New Class of Three-Body States," which was recently published in .

The state is similar to Efimov three-body states, a loosely-bound quantum state first predicted by Russian physicist Vitaly Efimov in the early 1970s. Physicists were able to first observe Efimov three-body states more than 30 years later through an experiment with ultracold atomic gases in 2006. These gases are one-billionth of a degree kelvin above -- a temperature that only exists in a handful of laboratories in the world. Esry said similar ultracold atomic gases are needed to observe their new quantum state as well since it can only exist at this temperature.

While Efimov three-body states only occur in ultracold conditions with atoms classified as bosons, the state found by Esry and colleagues applies to both bosons and fermions -- the two particle types that all matter can be classified as.

Additionally, the new quantum state exists in a pocket between short-ranged and long-ranged interactions. Short- and long-ranged interactions -- or forces -- are the distance at which the particle interactions are effective. With a long-ranged force, the particles have a greater distance between them and do not have to touch to interact and influence each other. With a short-ranged force, however, the particles must be in much closer proximity and interact similar to billiard balls colliding with one another, Esry said. The Efimov three-body states only exist for short-ranged interactions.

"The three-body states that we found are formed by interactions that are neither short- nor long-ranged," Esry said. "Instead, they lie right at the border between the two. So, more than anything, finding this new quantum state fills in a knowledge gap about three-body systems and quantum mechanics, which have been studied for centuries by physicists -- including Sir Isaac Newton studying the Earth, moon and sun."

Scientists may also find uses for the quantum state in experiments with ultracold .

"That's really the nature of basic research," Esry said. "We're trying things that hopefully will pay off for somebody 20 years or longer down the line. Efimov had to wait 35 years to see his actually be seen and used as a way to understand these three-body systems. We hope we don't have to wait that long."

Esry and colleagues will continue exploring this and to uncover how combinations of bosons and fermions behave in it.

Explore further

Physicists work to understand atomic collisions important to ultracold quantum gasses

Journal information: Physical Review Letters

Citation: Strength in numbers: Physicists identify new quantum state allowing three -- but not two -- atoms to stick together (2012, July 3) retrieved 25 August 2019 from
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Jul 03, 2012
Can anyone say, "Borromean Rings concept?"

Jul 03, 2012
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Jul 03, 2012
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Jul 04, 2012
InterPur offered this tidbit
Can anyone say, "Borromean Rings concept?"
Indeed, didnt know about that until your post, interesting, one wonders about the three quarks which make up the proton and the neutron and the various quantum interactions in QED, QCD etc and how that from above mirrors that from below etc as repeating patterns, good material for graphic lucid dreams, Christine and Mary and Mike and in colour ;-)


Jul 04, 2012
Can anyone say, "Borromean Rings concept?
Of course, Wikipedia explicitelly says "A quantum-mechanical analog of Borromean rings, called an Efimov state, was predicted by physicist Vitaly Efimov in 1970 .. In 2010, a team led by K. Tanaka created an Efimov state within a nucleus". My post about halo nuclei and explanation of it was deleted from here though. Apparently moderators who cannot understand this connection considered it as a pseudoscience (which is a bit funny, because mainstream physicists are doing money from public taxes wit it - but the laymans cannot talk about these connections, until moderators aren't aware of it too).

Jul 04, 2012
See Art Winfree, 1967. There are four stable states for three oscillator systems: three one third out of phase, three in sync, two exactly antisynchronous and the third twice as fast, and two in sync and one wild. Efimov state is three one third out of phase. Not sure what the exact pattern is for the result described in this article, but I bet it is one of these four Winfree patterns. Winfree stated his theory as a general mathematical proposition. He applied it to biological systems, but showed that his law applies generally to all systems of limit cycle oscillators. Gaits of a horse--trot, canter,gallop--follow his patterns for a four oscillator system.

Jul 04, 2012
Winfree's law described in Scientific American article, Dec 1993, by Steve Strogatz and Ian Stewart. "Coupled Oscillators and Biological Synchronization." Copy available on web at

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