Precursor of Superfluidity in a Strongly Interacting Fermi Gas with Negative Effective Range

TL;DR

This paper theoretically explores how pairing fluctuations induce a pseudogap in a strongly interacting ultracold Fermi gas with negative effective range, revealing the precursor to superfluidity and its implications for neutron matter.

Contribution

It introduces a many-body T-matrix approach to analyze pairing fluctuations and pseudogap phenomena in Fermi gases with negative effective range, extending understanding near narrow Feshbach resonances.

Findings

Identification of the pseudogap as a precursor to superfluidity.

Clarification of the role of strong pairing fluctuations across resonance regimes.

Extrapolation of fluctuation effects to positive effective range regions.

Abstract

We theoretically investigate the effects of pairing fluctuations in an ultracold Fermi gas near a Feshbach resonance with a negative effective range. By employing a many-body T-matrix theory with a coupled boson-fermion model, we show that the single-particle density of states exhibits the so-called pseudogap phenomenon which is a precursor of superfluidity induced by strong pairing fluctuations. We clarify the region where strong pairing fluctuations play a crucial role in single-particle properties, from the broad-resonance region to the narrow-resonance limit at the divergent two-body scattering length. We also extrapolate the effects of pairing fluctuations to the positive-effective-range region from our results near the narrow Feshbach resonance. Results shown in this paper are relevant to the connection between ultracold Fermi gases and low-density neutron matter from the viewpoint of finite-effective-range corrections.