Raman spectroscopy of Fermi polarons

TL;DR

This paper uses a non-self-consistent T-matrix approach to calculate finite-temperature Raman spectra of Fermi polarons, analyzing how spectrum features depend on various physical parameters and comparing with recent experiments.

Contribution

It provides a theoretical framework for Raman spectroscopy of Fermi polarons at finite temperature, including detailed dependence on momentum, temperature, and interaction, with comparison to experimental data.

Findings

Good agreement at weak coupling

Weaker impurity concentration dependence than RF spectroscopy

Discrepancies near Feshbach resonance at strong coupling

Abstract

By using a non-self-consistent many-body $T$-matrix theory, we calculate the finite-temperature Raman spectroscopy of a mobile impurity immersed in a Fermi bath in three dimensions. The dependences of the Raman spectrum on the transferred momentum, temperature, and impurity-bath interaction are discussed in detail. We confirm that the peak in the Raman spectrum shows a weaker dependence on the impurity concentration than that in the radio-frequency spectroscopy, due to the nonzero transferred momentum, as anticipated. We compare our theoretical prediction with the recent measurement by Gal Ness \textsl{et al.} in Physical Review X \textbf{10}, 041019 (2020) without any adjustable parameters. At weak coupling, we find a good quantitative agreement. However, close to the Feshbach resonance the agreement becomes worse. At strong coupling, we find that an unrealistic Fermi bath temperature might be needed, in order to account for the experimental data.