Researchers at JILA, a joint program of NIST and the University of Colorado at Boulder, recently announced that they achieved a temperature far lower than any previously produced and created an entirely new state of matter predicted 70 years ago by Albert Einstein and Indian physicist Satyendra Nath Bose.A paper in the July 14 Science by the researchers describe how the team cooled rubidium atoms to less than 170 nK above absolute zero.The extreme cold caused the individual atoms to condense into a ''superatom'' that behaved as a single entity.Before photographing the superatomknown as a Bose-Einstein condensate-the physicists cooled the atoms to 20 nK above absolute zero, the lowest temperature ever achieved.The achievement climaxed a 15 year search by physicists worldwide for the condensate.
Researchers at JILA, a joint program of NIST and the University of Colorado at Boulder, recently announced that they achieved a temperature far lower than any previously produced and created an entirely new state of matter predicted 70 years ago by Albert Einstein and Indian physicist Satyendra Nath Bose.A paper in the July 14 Science by the researchers describe how the team cooled rubidium atoms to less than 170 nK above absolute zero.The extreme cold caused the individual atoms to condense into a ''superatom'' that behaved as a single entity.Before photographing the superatomknown as a Bose-Einstein condensate-the physicists cooled the atoms to 20 nK above absolute zero, the lowest temperature ever achieved.The achievement climaxed a 15 year search by physicists worldwide for the condensate.
At 10.54 a.m. on Monday 5 June 1995 a group of physicists at the JILA laboratory in Boulder, Colorado, created something that had never been seen before – a Bose – Einstein condensate made of atoms. Eric Cornell, Carl Wieman and colleagues had made a new state of matter by cooling a gas of rubidium-87 atoms to a temperature of just 170 nK. This was so cold that the de Broglie wavelength of the atoms was comparable with the distance between them, causing the atoms to condense into the same quantum ground state. The breakthrough in Boulder kick-started an intense period of research into the properties of ultracold atoms that continues to this day, and has implications for topics as diverse as super-fluidity and the early universe.
The phenomenon of Bose-Einstein condensation (BEC), first predicted by Einstein 70 years ago, has finally been observed in the laboratory. In this elusive state of matter the concept of individual particles ceases to have meaning: the atoms condense into the same quantum state and act as a single entity that displays quantum mechanical behaviour on a macroscopic scale. The condensate was observed when Eric Cornell, Carl Wieman and colleagues at the Joint Institute for Laboratory Astrophysics in Boulder, Colorado, cooled a dilute gas of rubidium atoms, confined in a magnetic trap, to a temperature of just a few nanoKelvin (M H Anderson et al. 1995 Science 269 198).
A Bose-Einstein condensate (BEC), the first of which was shown experimentally 22 years ago, isn’t your garden variety state of matter. It formed at a fraction above absolute zero and only in atoms that act like bosons, one of two types of fundamental particles. Bosons don’t follow the Pauli exclusion principle, which prohibits two particles from existing in the same quantum state. When bosonic atoms are cooled to form a condensate, they can lose their individuality. They behave like one big collective superatom, analogous to how photons become indistinguishable in a laser beam. But it’s even weirder than that.
This velocity-distribution data for a gas of rubidium atoms confirmed the discovery of the Bose–Einstein condensate in 1995. In these three snapshots in time, atoms—cooled to near absolute zero—condensed from less dense areas on the left (red, yellow, and green) to very dense areas at the center and the right (blue and white). Image courtesy of NIST/JILA/CU-Boulder.
“In a very good analogy, one can view a BEC as a bell, which begins to ring spontaneously when it is cooled below a certain temperature,” writes physicist Nick Proukakis at the Joint Quantum Centre Durham–Newcastle in the United Kingdom, in Universal Themes of Bose–Einstein Condensation , a forthcoming collection of research essays on progress in BECs (1). That behavior provides physicists with an extraordinary opportunity: to study bizarre quantum effects on a large scale, instead of having to probe individual particles.
For the last two decades, physicists have treated BECs something like Play-Doh. They poke it, smash it, tickle it with lasers, and trap it in magnetic fields. They mix condensates together to see what happens, and use it to slow down light (2). They have observed strange behaviors that would have been impossible to predict even two decades ago: solids that flow …
About seven decades ago Satyendra Nath Bose and Albert Einstein predicted that a gas of noninteracting integer-spin particles would condense into a macroscopic quantum state when cooled below a critical temperature. Of course Bose–Einstein condensation (BEC) has long since been seen in superfluid He4 and superconductors, but the condensing systems in these examples are far from being noninteracting gases; relatively strong interactions between the condensing particles greatly complicate the theoretical analysis and the experimental behavior. For more than 15 years groups have been cooling and compressing clouds of atoms on a quest to produce and observe a Bose–Einstein condensate in a nearideal gas. They pushed their devices to the limit, seeking to traverse 15 orders of magnitude of phase-space density, and as each technique proved insufficient they developed ingenious variations to create ever colder and denser states.
A year ago this month, physicists first created a Bose-Einstein condensate, a state of matter in which a cloud of trapped atoms is cooled so close to absolute zero that their quantum-mechanical waves merge. But with barely 1000 atoms in a condensate that lasted just a few seconds, the researchers could do no more than say they'd done it. Now the field is being transformed by a new atom trap that can create condensates of 5 million sodium atoms that survive for half a minute and a new technique for imaging condensates without destroying them. Several research groups are now probing the size, growth rate, optical properties, and even the viscosity of this new form of matter.
A group at the University of Texas at Austin has recently created Rb\-2 moleculaes from a Rubidium\|87 Bose\|Einstein condensate with two\|photon stimulated Raman transitions.The molecules are in a single ro\|vibrational level and have a temperature on the order of 100nK.These might be the coldest molecules in the universe,as says Paul Julienne,a senior atomic physicist at NIST.This method provides an alternative route for formation of ultra\|cold molecules which are still not achievable with the traditional laser cooling and trapping techniques,and may lead to the first realization of molecular Bose\|Einstein condensate.