Evolution of the Normal State of a Strongly Interacting Fermi Gas from a Pseudogap Phase to a Molecular Bose Gas

TL;DR

This paper investigates how a strongly interacting ultracold Fermi gas transitions from a pseudogap phase to a molecular Bose gas, using rf spectroscopy and pairing-fluctuation theory, revealing the disappearance of the Fermi surface with increasing interaction.

Contribution

It provides a detailed mapping of the evolution from pseudogap to molecular Bose gas and validates the pseudogap theory against experimental and Quantum Monte Carlo data.

Findings

Disappearance of the Fermi surface at strong coupling

Consistency of pseudogap theory with experimental data

Agreement with Quantum Monte Carlo thermodynamics

Abstract

Wave-vector resolved radio frequency (rf) spectroscopy data for an ultracold trapped Fermi gas are reported for several couplings at Tc, and extensively analyzed in terms of a pairing-fluctuation theory. We map the evolution of a strongly interacting Fermi gas from the pseudogap phase into a fully gapped molecular Bose gas as a function of the interaction strength, which is marked by a rapid disappearance of a remnant Fermi surface in the single-particle dispersion. We also show that our theory of a pseudogap phase is consistent with a recent experimental observation as well as with Quantum Monte Carlo data of thermodynamic quantities of a unitary Fermi gas above Tc.