Topological defect for Bose-Einstein condensates found during phase transition

Oct 17, 2008 07:47 GMT  ·  By

American and Australian researchers have discovered that, when a supercooled gas is cooled even further, it enters a phase transition where a number of atoms gather into a Bose-Einstein condensate. Depending on the gas and its temperatures, the atoms begin to spin rapidly, forming a quantum tornado. This allows scientists to further investigate the laws of physics, while it may also lead to new concepts for the development of a number of devices.

 

A phase transition is a process that is very frequent in nature and human life, ranging from the water vaporizing or freezing, to the change in an egg's structure when boiled or fried. The same thing happens to an extra-cool gas when it is subjected to even lower temperatures.

 

Based on the theoretical calculations of the researchers at the University of Queensland in Australia, Brian P. Anderson and his team from the University of Arizona found that, while trapping rubidium gases and cooling them to approximately 50 billionths of a degree Kelvin (around -460 degrees Fahrenheit or -273.15 degree Celsius) from a previously somewhat warmer temperature, with the help of magnetic fields and precise lasers, something strange happens with the atoms of the gas. While some of them still obey the laws of regular physics and keep bouncing randomly, others tend to aggregate into a novel matter dubbed a Bose-Einstein condensate (BEC – first discovered in 1995), which rather acts by the laws of quantum physics.

 

However the American-Australian team of experts also found that a new thing, which they named “topological defect,” was occurring during the phase transition phenomenon. “In our experiments, we found that when we cool an already very cold gas through the BEC phase transition, the BEC can spontaneously begin to rotate, creating something like a microscopic quantum mechanical hurricane where atoms rotate as a fluid around a vortex core where there is no fluid,” explained Anderson.

 

“What was so surprising about our work is that we saw these things just appear by themselves. You just make your condensate, and they sometimes appear. You don't have to somehow manipulate your system, all you have to do is cool through the phase transition. By collaborating with our colleagues in Australia, who are doing the theoretical research, we can back out details of the physical process that causes these vortices to spontaneously form. It will help us understand more about how superfluids develop, and perhaps more about universal phase transition dynamics in general, including the kind of phase transition that occurred in the early universe,” he added.

 

Anderson envisions interferometers, accelerometers, rotation sensors and other applications built by means of BECs, while they could also aid scientists understand more about how physics works and how the universe formed.