Spin polarons and molecules in strongly-interacting atomic Fermi gases

TL;DR

This paper investigates pairing, molecule formation, and quasiparticle behavior in strongly-interacting atomic Fermi gases, demonstrating how RF spectroscopy can reveal these phenomena and providing insights into the properties of spin polarons and molecules.

Contribution

It provides a detailed analysis of RF spectra in strongly-interacting Fermi gases, highlighting the formation of molecules and spin polarons across different regimes, with new insights into their spectral signatures.

Findings

Stable molecules produce a two-peak RF spectrum in the BEC regime.

Existence of well-defined spin polarons in highly-imbalanced gases.

RF spectroscopy can measure polaron energies and lifetimes.

Abstract

We examine pairing and molecule formation in strongly-interacting Fermi gases, and we discuss how radio-frequency (RF) spectroscopy can reveal these features. For the balanced case, the emergence of stable molecules in the BEC regime results in a two-peak structure in the RF spectrum with clearly visible medium effects on the low-energy part of the molecular wavefunction. For the highly-imbalanced case, we show the existence of a well-defined quasiparticle (a spin polaron) on both sides of the Feshbach resonance, we evaluate its lifetime, and we illustrate how its energy may be measured by RF spectroscopy.