'Vortex lattice' can help explain material errors

What do you get when superimposing a rotating image of lasers intersecting on a circular cloud with ultracold atoms in a thin layer of gas? what you achieve is not only beautiful pictures but also a new method that can be used to replicate by model, which helps explain why and how the errors arise in super Lead, an important material that is difficult to study directly.

By combining the two most recent laboratory objects - optical lattices and optical atoms in a material called Bose-Einstein Condensate (BEC) rotates in a trap like the onions. The crystal turns in orbit around the sun - physicists at JILA have developed a method that can help visualize the defects or defects of matter through rotating images.

The JILA photo gallery gave Bose-Einstein condensate material (BEC) a ' pinning ' of the spinning computer network created by lasers, when the shape of the ' vortex lattice ' combined, evolving a shaped word triangle (above) into a square shape (below) . The images on the left show the BEC vortex lattice rotating with low, medium and high optical intensity (top down) . The corresponding images on the right are computer images processing, showing the structural relationship between the vortex and the crystal strength of BEC matter with the symmetry of the physical structure shown in red (in the form Hexagon, triangle and square) (Photo: Cornell / JILA Team).

These experiments were published in a paper published in Physical Review Letters online on December 12, experiments that yielded the ' tornado in the valley', leader Eric Cornell, academician at NIST National Institute of Standards and Technology said. JILA Institute is the collaboration between the NIST Institute and the University of Colorado at Boulder.

Bose-Einstein Condensate matter is a unique form of matter , first created by Cornell and colleague Carl Wieman at JILA. In this matter, atoms are cooled to near absolute zero (absolute zero) and at the point where according to quantum physics rules the atoms will condense into an infinite 'super atom'. the figure in which the super atom, cannot distinguish individual atoms.

Part of the scientific charm of BEC material is that they have the same important physical properties with seemingly completely different phenomena, such as low energy pair electrons in good superconductors. ' superfluid ' (helium-4 " superfluid "), an extremely dilute substance, without obstructing the flow of liquid fluid (kinematic viscosity = 0), friction between molecules in a liquid solution same small (considered as zero) and without surface tension. For example, helium-4, does not circulate around its container like water in a glass, but breaks the sequence of quantized vortices or small tornadoes. And BEC material has the same properties.

The JILA experiments were performed with 3 million rubidium atoms in a magnetic trap. The vortex of the vortex is created by spinning the trap. The red BEC cloud, about 100 micrometers in diameter, contains about 100 sunken vortices, like a spinning bundle of fibers. The lasers used to establish optical lattices are in the form of triangles and squares and converge these lattices to BEC material.

The lattice and swirling funnels overlap and under certain conditions such as when they spin at nearly the same speed, they tend to stick together. The energy peak of the lattice will ' pin ' the BEC material to those points by reducing the density of the superfluid flowing around the local vortex.

The JILA team visualized the structure or repetitive images of spinning vortices by taking photos in experiments and then using image processing techniques to see how the structure and The lattice orientation of the vortex lends itself to the structure and orientation of the optical lattice. Vortex lattice and peak optical signals evolved into different shapes, at different laser intensities and rotational speeds. Because matter of BEC and optical lattices can be precisely controlled, this new technique could be useful in studying more mysterious 'superfluids' such as superconductors. lead such.

Thanh Van