from the earl-grey,-hot,-please dept.
According to a press release (3 January 2002), researchers at the Max-Planck-Institute for Quantum Optics in Garching and at the Ludwig-Maximilians University of Munich have been able to manipulate atoms in a Bose-Einstein condensate with an optical lattice, allowing them to create a new phase of matter with an exact number of atoms at each lattice site. The researchers observed the phase transition between two dramatically different states of matter close to temperatures of absolute zero.
In a Bose-Einstein condensate, the atoms loose their individuality and a wave-like state of matter is created that can be compared in many ways to laser light. In the new work, the scientists store a Bose-Einstein condensate in a three-dimensional lattice of microscopic light traps. By increasing the strength of the lattice, the researchers are able to dramatically alter the properties of the dilute gas of atoms and induce a quantum phase transition from the superfluid phase of a Bose-Einstein condensate to a Mott insulator phase.
For a weak optical lattice the atoms form a superfluid phase of a Bose-Einstein condensate. In this phase, each atom is spread out over the entire lattice in a wave-like manner as predicted by quantum mechanics. The gas of atoms may then move freely through the lattice. For a strong optical lattice the researchers observe a transition to an insulating phase, with an exact number of atoms at each lattice site. Now the movement of the atoms through the lattice is blocked due to the repulsive interactions between them. The researchers were also able to show that it is possible to reversibly cross the phase transition between these two states of matter.