Laser traps hel¥researchers observe new state of matter
A fundamentally new state of matter, predicted in 1924 by Albert Einstein and Indian physicist Satyendra Nath Bose, has been produced by Eric Cornell and Carl Wieman of JILA (Boulder, CO). In a demonstration of a classical problem in statistical thermodynamics in which atoms below a certain very low temperature would collectively dro¥into the lowest-energy quantum-mechanical state, the Colorado team used six laser beams and magnetic fields to observe rubidium "superatoms" in a shared quantum state, analogous to superconductivity and superfluidity. They observed the condensate when temperature dropped below 170 nK, and the density of their tiny sample--only about 2000 atoms--was 2.5 ¥ 1012 atoms/cm3.
The tiny ball, which in false-color images looks like the pit in a cherry, was surrounded by other rubidium atoms and survived for at least 15 seconds. "This state could never have existed naturally anywhere in the universe, so the sample in our lab is the only chunk of this stuff," said Cornell. The atoms "are as close to absolute zero as the laws of science will allow," added Wieman. They and three colleagues reported details--including cooling a sample to a record low temperature of 20 nK--in the 14 July 1995 issue of Science.