:: OSEL.CZ :: – Bose-Einstein condensate in free fall broke record low temperature

The Bose-Einstein condensate freely broke through a record low temperature

Drop tower Bremen. Credit: Am In The Garden / Wikimedia Commons.

A temperature of minus 273.15 ° C, or absolute zero, the lowest possible temperature on a thermodynamic scale, represents a state in which there is no heat at all. Atoms absolutely freeze in motion. But this is a theoretical limit, because, as far as we know, it is not possible to take all the kinetic energy from atoms.

Scientists seem to respect that. At the same time, however, the nail teeth try to get as close as possible to the absolutely low temperature. And they have already done wonderful things in this direction. A few years ago, the American team at Harvard studied the coldest chemical reaction we have ever measured, at a temperature of 500 nanokelvins. And the remarkable Cold Atom Lab has been working on board the ISS for several years, experimenting with 100 nanokelvins.

Logo.  Credit: University of Bremen.

Logo. Credit: University of Bremen.

However, these very decently low temperatures have now been spread on bread by the German scientists of the QUANTUS 2 project team from the University of Bremen, who in their wonderful experiment reached a temperature of an incredible 38 picolequins, or 38 trillionths of Kelvin.

The QUANTUS 2 project team in a good mood.  Credit: University of Bremen.

The QUANTUS 2 project team in a good mood. Credit: University of Bremen.

How did they do it? First, they formed a cloud of about 100,000 rubidium atoms, which was trapped in a magnetic field, inside a vacuum chamber. This cloud was then frozen to form the popular Bose-Einstein condensate, a special state of matter in the form of a quantum gas, whose atoms behave as if they were a single atom. In the Bose-Einstein condensate, bizarre quantum phenomena manifest themselves on a relatively large scale.

However, the QUANTUS 2 team did not end there. They took the Bose-Einstein condensate and experimented with it on the remarkable 120-meter-high Fallturm Bremen tower, which is part of the Zentrum für angewandte Raumfahrttechnologie und Mikrogravitation (ZARM) at the University of Bremen. Scientists are having fun by letting everything possible fall freely and researching it intensively. QUANTUS 2 dropped a vacuum chamber with a Bose-Einstein condensate there. During the free fall, researchers repeatedly turned on and off the magnetic field that surrounds the Bose-Einstein condensate.

When the magnetic field was turned off, the Bose-Einstein condensate expanded. After turning on the magnetic field, it shrunk again. In this way, scientists have managed to limit the movements of BE condensate atoms to such an extent that they have reached a record low temperature. In the experiments, they succeeded for a maximum of 2 seconds. Simulations show that with this procedure, it would be possible to maintain such a temperature for up to 17 seconds if the experiments were performed in a non-gravitational environment, such as aboard a satellite.

Video: The Bremen Drop Tower – What’s inside?

Literature

New Atlas 9. 9. 2021.

Physical Review Letters 127: 100401.

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