Physicists from Ludwig-Maximilians University Munich and the Max Planck Institute of Quantum Optics in Garching have generated an atomic gas with negative Kelvin values in their laboratory, leading to various ludicrous outcomes.
One such outcome is the gas remaining uncollapsed, similar to the proposed behaviour of dark energy in cosmology. The gas is not colder than zero Kelvin, but rather hotter than any positive temperature.
The inverted Boltzmann distribution, which represents the distribution of energy in a gas, is characteristic of negative absolute temperature. This inversion indicates that the particles have a negative absolute temperature. The gas is not colder than zero Kelvin, but rather hotter than any positive temperature.
A negative absolute temperature can only be attained with an upper restriction on energy. Immanuel Bloch and Ulrich Schneider's research group successfully developed an atomic gas system with an upper energy limit in their laboratory. They first cool around a hundred thousand atoms in a vacuum chamber to a positive temperature of a few billionths of a Kelvin before capturing them in optical traps built of lasers. The laser beams form an optical lattice, which atoms can travel from one location to another using the tunnel effect, but their kinetic energy is limited. This system limits both the kinetic energy and total energy of the particles, resulting in a negative temperature of minus a few billionths of a Kelvin.
Researchers at Munich University revealed that particles can do more work at negative temperatures than positive temperatures. This discovery could lead to the development of heat engines with above 100% efficiency, allowing them to collect energy from both hotter and colder mediums. This is because at negative temperatures, the hot medium can absorb energy from both media at the same time, resulting in more work performed by the engine than energy obtained from the hotter medium alone.
Such discoveries and developments may also be applied in cosmology. The thermodynamic behaviour of negative temperatures is similar to dark energy, which is thought to accelerate the expansion of the universe. The experiment is based on the attraction interaction of atoms in the atomic cloud, which keeps the gas from collapsing due to its negative temperature.
Works Cited
ScienceDaily. (2024). A temperature below absolute zero: Atoms at negative absolute temperature are the hottest systems in the world. [online] Available at: https://www.sciencedaily.com/releases/2013/01/130104143516.htm. [Accessed 8 Mar. 2024].
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