Synopsis: Dipolar Gas Chilled to Near Zero

The cooling of strongly dipolar molecules to their absolute ground state has opened the possibility of creating new forms of matter.
Synopsis figure
Jee Woo Park and Sebastian Will/MIT

Cooling dipolar molecules to near absolute zero could produce new quantum states of matter, as the dipoles exert strong long-range forces on each other that are not found in nature. Researchers have now chilled a gas of sodium-potassium (NaK) molecules in their absolute ground state to microkelvin temperatures. The NaK molecules have a stronger dipole interaction and are more stable than previous superchilled molecules, which makes them ideal for exploring the impact of dipolar interactions in the quantum regime.

Molecules differ from atoms in that they rotate and vibrate. These extra degrees of freedom complicate efforts to cool molecules with traditional laser techniques. To circumvent these challenges, researchers have recently been able to form certain ultracold molecules—the fermionic KRb and the bosonic RbCs—directly out of a gas of ultracold atoms, and to subsequently transfer them into their rovibrational ground state.

Martin Zwierlein and his colleagues at MIT have added the fermionic NaK to this small class of ultracold molecules. The team started with cold sodium and potassium atoms and then used a magnetic field to access a so-called Feshbach resonance that combines the atoms into weakly bound molecules. Subsequently, a pair of lasers couples this Feshbach state to the rovibrational ground state, allowing a smooth transfer to the lowest energy state without adding kinetic energy to the gas. Because NaK doesn’t easily dissociate, the team found it has a relatively long lifetime (greater than 2.5 seconds), which benefits future experiments. If the temperature can be lowered by another order of magnitude, the NaK gas will enter the quantum degenerate regime where exotic forms of matter are predicted, such as a topological superfluid that contains Majorana fermions or a dipolar quantum crystal that could be solid and superfluid at the same time.

–Michael Schirber

This research is published in Physical Review Letters.


Features

More Features »

Announcements

More Announcements »

Subject Areas

Atomic and Molecular Physics

Previous Synopsis

Next Synopsis

Biological Physics

Water Flow Helps Cells Move

Read More »

Related Articles

Synopsis: Direct View of Exchange Symmetry
Quantum Physics

Synopsis: Direct View of Exchange Symmetry

A proposed set of experiments could offer a direct measurement of the fundamental quantum property that distinguishes fermions from bosons. Read More »

Synopsis: Topological Defect on the Move
Condensed Matter Physics

Synopsis: Topological Defect on the Move

Researchers have directed the motion of a domain-wall-like topological defect through a crystal of trapped ions. Read More »

Viewpoint: Trapped Ions Test Fundamental Particle Physics
Atomic and Molecular Physics

Viewpoint: Trapped Ions Test Fundamental Particle Physics

New precision experiments using trapped molecular ions provide an alternative method for determining if the electron has an electric dipole moment. Read More »

More Articles