We employ radio-frequency spectroscopy to investigate a polarized spin mixture of ultracold Li-6 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*, 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* diverges and even turns negative, thereby indicating that the repulsive Fermi liquid state becomes energetically and thermodynamically unstable.
Repulsive Fermi Polarons in a Resonant Mixture of Ultracold Li-6 Atoms / Scazza, F., Valtolina, G., Massignan, P., Recati, A., Amico, A., Burchianti, A., Fort, C., Inguscio, M., Zaccanti, M., Roati, G.. - In: PHYSICAL REVIEW LETTERS. - ISSN 0031-9007. - 118:8(2017). [10.1103/PhysRevLett.118.083602]
Repulsive Fermi Polarons in a Resonant Mixture of Ultracold Li-6 Atoms
Scazza F;
2017-01-01
Abstract
We employ radio-frequency spectroscopy to investigate a polarized spin mixture of ultracold Li-6 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*, 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* diverges and even turns negative, thereby indicating that the repulsive Fermi liquid state becomes energetically and thermodynamically unstable.Pubblicazioni consigliate
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