Cesium atoms must be shaken, not stirred.

• Position: Superconductors

Scientists discovered in 1937 that liquid helium-4, when chilled to extremely low temperatures, became a superfluid that could leak through glass, overflow its containers, or eternally gush like a fountain.

Future Nobel laureate Lev Landau, a Soviet physicist, came along in 1941, predicting that superfluid helium-4 should contain an exotic, particle-like excitation called a roton, but scientists--including Landau, Nobel laureate Richard Feynman, and Wolf Prize recipient Philippe Nozieres--have debated what structure the roton would take ever since.

"Even nowadays, after seven decades, it remains an issue of interest and controversy," says physicist Cheng Chin in a paper published in Physical Review Letters. Chin and four associates describe how they can create roton structure in a new system: atomic superfluid of cesium-133 in the laboratory.

Scientists who specialize in superfluids have found it difficult to study rotons. Chin's team has pioneered a system that will make it much easier to reveal the long-cloaked mysteries of the roton. The researchers generated artificial rotons using what they call the shaken lattice technique, creating a superfluid in a one-foot cylindrical chamber cooled to a temperature of approximately 15 nano-Kelvin, just a tiny fraction of a degree above absolute zero (minus-459.6[degrees]F).

During the experiment, 30,000 cesium atoms became trapped in a crossing pattern of infrared laser beams. This optical lattice holds the atoms fast, like eggs in a crate, while gently shaking them. "We need about 10 seconds to reach that temperature to prepare a superfluid as our first step," Chin explains. "It is a brand new idea that shaking the optical lattice leads to the emergence of the rotons."

The superfluid persists for several seconds, during which time the physicists create the roton structure and image it to see how the structure influences the superfluid's properties...