Pauli blocking of light scattering in degenerate fermions

TL;DR

This paper demonstrates the suppression of light scattering in a quantum-degenerate Fermi gas of ultracold lithium atoms, confirming long-standing predictions about Pauli blocking effects on elastic and inelastic light scattering.

Contribution

First experimental observation of Pauli blocking of light scattering in a degenerate Fermi gas of ultracold atoms.

Findings

Light scattering is suppressed at low temperatures in a dense Fermi gas.

Suppression of inelastic light scattering during atomic collisions was observed.

The results confirm theoretical predictions about Pauli blocking effects.

Abstract

Pauli blocking of spontaneous emission is responsible for the stability of atoms. Higher electronic orbitals cannot decay to lower-lying states if they are already occupied -- this is Pauli blocking due to occupation of internal states. Pauli blocking also occurs when free atoms scatter light elastically (Rayleigh scattering) and the final external momentum states are already occupied. A suppression of the total rate of light scattering requires a quantum-degenerate Fermi gas with a Fermi energy larger than the photon recoil energy. This has been predicted more than 30 years ago, but never realized. Here we report the creation of a dense Fermi gas of ultracold lithium atoms and show that at low temperatures light scattering is suppressed. We also explore the suppression of inelastic light scattering when two colliding atoms emit light shifted in frequency.