Comparison of spectral linewidths for quantum degenerate bosons and fermions

Abstract

We observe a dramatic difference in optical line shapes of a ${}^4\text{He}$ Bose-Einstein condensate and a ${}^3\text{He}$ degenerate Fermi gas by measuring the 1557-nm $2{}^{3}S-2{}^{1}S$ magnetic dipole transition ($8\text{Hz}$ natural linewidth) in an optical dipole trap. The $15\text{kHz}$ FWHM condensate line shape is only broadened by mean field interactions, whereas the degenerate Fermi gas line shape is broadened to $75\text{kHz}$ FWHM due to the effect of Pauli exclusion on the spatial and momentum distributions. The asymmetric optical line shapes are observed in excellent agreement with line shape models for the quantum degenerate gases. For ${}^4$He a triplet-singlet s-wave scattering length $a=+50(10{)}_{\text{stat}}(43{)}_{\text{syst}}{a}_0$ is extracted. The high spectral resolution reveals a doublet in the absorption spectrum of the BEC, and this effect is understood by the presence of a weak optical lattice in which a degeneracy of the lattice recoil and the spectroscopy photon recoil leads to Bragg-like scattering.

5 pages, 4 figures, 5 pages supplemental information

References in corpus (6)

• Many-Body Physics with Ultracold Gases
• Camparison of the Hanbury Brown-Twiss effect for bosons and fermions
• Spectroscopic insensitivity to cold collisions in a two-state mixture of fermions
• A Degenerate Bose-Fermi Mixture of Metastable Atoms
• High-precision spectroscopy of the forbidden 2 3S1 - 2 1P1 transition in quantum degenerate metastable helium
• Magic wavelengths for the $2{}^{3}S\to 2{}^{1}S$ transition in helium

Cited by in corpus (5)

• Dynamics of spatially indistinguishable particles and entanglement protection
• Pauli blocking of stimulated emission in a degenerate Fermi gas
• Generation of genuine multipartite entangled states via indistinguishability of identical particles
• Production of a highly degenerate Fermi gas of metastable helium-3 atoms
• Frequency measurements of transitions from the $2^3{P}_2$ state to the $5^1{D}_2$, $5^3{S}_1$, and $5^{3}D$ states in ultracold helium