Repulsive Fermi polarons in a resonant mixture of ultracold ${}^6$Li atoms

Abstract

We employ radio-frequency spectroscopy to investigate a polarized spin-mixture of ultracold ${}^6$Li atoms close to a broad Feshbach scattering resonance. Focusing on the regime of strong repulsive interactions, we observe well-defined coherent quasiparticles even for unitarity-limited interactions. We characterize the many-body system by extracting the key properties of repulsive Fermi polarons: the energy $E_{+}$, the effective mass $m^{\ast }$, the residue $Z$ and the decay rate $\Gamma$. Above a critical interaction, $E_{+}$ is found to exceed the Fermi energy of the bath while $m^{\ast }$ diverges and even turns negative, thereby indicating that the repulsive Fermi liquid state becomes energetically and thermodynamically unstable.

6 + 12 pages, 4 + 6 figures, 57 references

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Cited by in corpus (9)

• Observation of a Degenerate Fermi Gas Trapped by a Bose-Einstein Condensate
• Universality of the unitary Fermi gas: A few-body perspective
• Coherent Oscillations in Small Fermi Polaron Systems
• Enhancing the Efimov correlation in Bose polarons with large mass imbalance
• Hartree-Fock treatment of Fermi polarons using the Lee-Low-Pine transformation
• Bipolarons bound by repulsive phonon-mediated interactions
• Three in Many: Efimov physics in the presence of a Fermi sea
• Repulsive Fermi polarons with negative effective mass
• A mixed dimensional Bose polaron