Amazing stuff!
"... In their experiments, the physicists observed this effect in a cloud of lithium atoms. As they were made colder and more dense, the atoms scattered less light and became progressively dimmer. The researchers suspect that if they could push the conditions further, to temperatures of absolute zero, the cloud would become entirely invisible. The team’s results, reported today in Science, represent the first observation of Pauli blocking’s effect on light-scattering by atoms. This effect was predicted 30 years ago but not observed until now. ... This is the first clear observation that this effect exists, and it shows a new phenomenon in physics. ..."
From the abstract:
"Pauli blocking occurs when free atoms scatter light elastically and the final external momentum states are already occupied. Suppression of the total rate of light scattering requires a quantum-degenerate Fermi gas with a Fermi energy larger than the photon recoil energy. Pauli blocking was predicted 30 years ago, but the experimental realization was elusive due to the difficulty of prepare cold fermi gas at high density. Here we report the creation of a dense Fermi gas of ultracold lithium atoms and show that at low temperature light scattering is suppressed. We also demonstrated the suppression of inelastic light scattering when two colliding atoms emit light shifted in frequency. Our platform enables future studies of light-matter interaction at high density."
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