Bragg Spectroscopy of Cold Atomic Fermi Gases

TL;DR

This paper proposes using Bragg spectroscopy to detect superfluid pairing in ultracold Fermi gases, revealing the pairing gap and pseudogap effects across different interaction regimes.

Contribution

It introduces a novel experimental approach to measure superfluid pairing and analyze spectral features in ultracold Fermi gases across various coupling strengths.

Findings

Bragg spectrum shows a gap related to pair-breaking energy.

Large maximum in spectrum appears below critical temperature in BCS regime.

Pseudogap suppresses low-frequency spectrum in unitarity regime.

Abstract

We propose a Bragg spectroscopy experiment to measure the onset of superfluid pairing in ultracold trapped Fermi gases. In particular, we study two component Fermi gases in the weak coupling BCS and BEC limits as well as in the strong coupling unitarity limit. The low temperature Bragg spectrum exhibits a gap directly related to the pair-breaking energy. Furthermore, the Bragg spectrum has a large maximum just below the critical temperature when the gas is superfluid in the BCS limit. In the unitarity regime, we show how the pseudogap in the normal phase leads to a significant suppression of the low frequency Bragg spectrum.