Scientists Create New Form of Matter
IN what is being described as a major breakthrough in physics, scientists have created a unique form of matter by chilling atoms to within a few billionths of a degree of absolute zero.
Using lasers, magnets, and their wits, the researchers appear to have proven a theory first proposed by Albert Einstein and Indian physicist Satyendra Nath Bose 70 years ago.
The breakthrough, if true, could lead to the development of ''atom lasers'' that may significantly aid efforts to build smaller microchips and better navigation systems. It could also boost research in important fields such as superconductivity, the development of materials that conduct electricity without resisting its flow.
Yesterday, scientists from the National Institute of Standards and Technology and the University of Colorado at Boulder announced the creation of the new phase of matter in minute quantities.
At unimaginable temperatures found nowhere in nature, collections of atoms in a gas stopped moving helter-skelter and began to act coherently as if they were a single atom, similar to the way light forms a laser. For lack of a better term, one scientist has simply dubbed the new matter ''atom stuff.''
The results of the experiment, conducted in June, appear in today's issue of the journal Science.
On Wednesday morning, a team from Rice University in Houston ran a similar experiment and got similar results, according to Randall Hulet, the physicist who led Rice's effort.
It was ''spectacular,'' says Daniel Kleppner, a Massachusetts Institute of Technology physicist, of the Colorado team's effort. ''Often, initial experiments are ambiguous. Their very first observation was as good as it can be.''
''There is a collective feeling that this is a real breakthrough,'' says Oxford University physicist Keith Burnett.
On one level, the experiments confirmed a theory first proposed by Einstein and Nath Bose. In the bizarre world of quantum physics, atoms behave like waves as well as like particles.
When viewed as waves, atoms have an equivalent wavelength that grows as the atom's momentum slows. The two scientists reasoned that at some low temperature, those wavelengths would begin to span the distance between atoms and overlap. When that happened, one atom would become indistinguishable from the rest - all the atoms in the system would be in the same quantum state, acting coherently. The phenomenon became known as Bose-Einstein condensation (BEC).
On another level, the discovery of a new phase of matter opens the door to speculation on how to use it. ''Imagine that you have a laser - an amplifier and two mirrors that reflect 99 percent of the light back and forth. The other 1 percent of light escapes as the laser beam. We would like to do the same thing with atoms,'' says David Prichard, another physicist at MIT, in Cambridge, Mass.
If such atom lasers can be developed, they could aid efforts to build smaller semiconductors and machines (such as tiny motors), and increasingly accurate navigation systems. ''But for now,'' he quickly adds, ''this is a newborn baby.''
NATIONAL Institute of Standards and Technology physicist Eric Cornell (Dr. Prichard's former student) and his colleagues achieved their results by bombarding a tenuous gas of rubidium atoms in a glass cell with six lasers, similar to those found in compact-disc players.
Dr. Cornell explains that because light exerts a slight pressure, the team used the lasers to form what he calls ''optical molasses'' - no matter which way the atom tried to move, a laser beam was there to slow it.
Laser cooling only took the team so far, however - some tens of millionths of a degree above absolute zero. They turned to evaporation to cool the sample the rest of the way. By confining the gas in a rotating, bowl-like magnetic field, they were able to capture the coldest atoms at the bottom, while allowing the hotter atoms to escape. The design allowed them to achieve the temperatures and densities needed for BEC.
Cornell and others are planning follow-up experiments to answer basic questions about their ''atom stuff.'' Among them: Is this form of matter opaque or transparent to light? What are its magnetic properties?
''This is opening a new field of condensed-matter physics,'' Dr. Kleppner concludes.