Contact: Ulrich Schneider
Caption: Hot minus temperatures: At a negative absolute temperature the energy distribution of particles inverts in comparison to a positive temperature. Many particles then have a high energy and few a low one. This corresponds to a temperature which is hotter than one that is infinitely high, where the particles are distributed equally over all energies. A negative Kelvin temperature can only be achieved experimentally if the energy has an upper limit, just as non-moving particles form a lower limit for the kinetic energy at positive temperatures -- physicists at the LMU and the Max Planck Institute of Quantum Optics have now achieved this.
Credit: LMU and MPG Munich
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