Breakdown of Fermi liquid description for strongly interacting fermions

Abstract

The nature of the normal state of an ultracold Fermi gas in the BCS-BEC crossover regime is an intriguing and controversial topic. While the many-body ground state remains a condensate of paired fermions, the normal state must evolve from a Fermi liquid to a Bose gas of molecules as a function of the interaction strength. How this occurs is still largely unknown. We explore this question with measurements of the distribution of single-particle energies and momenta in a nearly homogeneous gas above $T_c$. The data fit well to a function that includes a narrow, positively dispersing peak that corresponds to quasiparticles and an "incoherent background" that can accommodate broad, asymmetric line shapes. We find that the quasiparticle's spectral weight vanishes abruptly as the strength of interactions is modified, which signals the breakdown of a Fermi liquid description. Such a sharp feature is surprising in a crossover.

arXiv comment21 pages including 4 main figures and a supplementary section with 5 extended data figures

References in corpus (33)

• Feshbach Resonances in Ultracold Gases
• Angle-resolved photoemission spectroscopy of the cuprate superconductors
• Observation of resonance condensation of fermionic atom pairs
• BCS-BEC Crossover: From High Temperature Superconductors to Ultracold Superfluids
• Large momentum part of fermions with large scattering length
• Observation of Fermi Polarons in a Tunable Fermi Liquid of Ultracold Atoms
• Exploring the Thermodynamics of a Universal Fermi Gas
• Using photoemission spectroscopy to probe a strongly interacting Fermi gas
• The Equation of State of a Low-Temperature Fermi Gas with Tunable Interactions
• Fermi-Polaron: Diagrammatic Monte Carlo for Divergent Sign-Alternating Series
• Observation of pseudogap behavior in a strongly interacting Fermi gas
• Universal Spin Transport in a Strongly Interacting Fermi Gas
• BCS-BEC Crossover and the Unitary Fermi Gas
• Verification of universal relations in a strongly interacting Fermi gas
• Polaron to molecule transition in a strongly imbalanced Fermi gas
• Breakdown of Fermi-liquid theory in a cuprate superconductor
• Spectral Functions and rf Response of Ultracold Fermionic Atoms
• Measurement of the Homogeneous Contact of a Unitary Fermi gas
• Evolution of the Normal State of a Strongly Interacting Fermi Gas from a Pseudogap Phase to a Molecular Bose Gas
• Exact Relations for a Strongly-interacting Fermi Gas near a Feshbach Resonance
• Fermi-Liquid Behavior of the Normal Phase of a Strongly Interacting Gas of Cold Atoms
• The Finite Temperature Pairing Gap of a Unitary Fermi Gas by Quantum Monte Carlo Calculations
• Radio-Frequency Transitions on Weakly-Bound Ultracold Molecules
• Temperature dependence of the contact in a unitary Fermi gas
• Analytical theory of the dressed bound state in highly polarized Fermi gases
• Universal Short-Distance Structure of the Single-Particle Spectral Function of Dilute Fermi Gases
• Temperature and coupling dependence of the universal contact intensity for an ultracold Fermi gas
• Radio frequency spectroscopy of a strongly imbalanced Feshbach-resonant Fermi gas
• Theory of Radio Frequency Spectroscopy Experiments in Ultracold Fermi Gases and Their Relation to Photoemission Experiments in the Cuprates
• Bragg Spectroscopy of Cold Atomic Fermi Gases
• Direct observation of the Fermi surface in an ultracold atomic gas
• Hartree shift in unitary Fermi gases
• Spin Transport in Cold Fermi gases: A Pseudogap Interpretation of Spin Diffusion Experiments at Unitarity

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• Viscosity Bound Violation in Viscoelastic Fermi Liquids
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