Pairing fluctuation effects in a strongly coupled color superfluid/superconductor

TL;DR

This paper studies how pairing fluctuations affect the unpaired color in strongly coupled three-component fermionic superfluids and superconductors, revealing temperature-dependent spectral behaviors including Fermi-liquid and pseudogap features.

Contribution

It introduces a pairing-fluctuation theory to analyze the unpaired color in three-component fermionic superfluids and superconductors, highlighting the temperature evolution of spectral properties.

Findings

At low temperature, the unpaired color shows a Fermi-liquid peak.

With increasing temperature, a three-peak spectral structure emerges.

Above the transition temperature, all colors exhibit pseudogap-like spectra.

Abstract

We investigate the effects of pairing fluctuations in fermionic superfluids/superconductors where pairing occurs among three species (colors) of fermions. Such color superfluids/superconductors can be realized in three-component atomic Fermi gases and in dense quark matter. The superfluidity/superconductivity is characterized by a three-component order parameter which denotes the pairing among the three colors of fermions. Due to the SU$(3)$ symmetry of the Hamiltonian, one color does not participate pairing. This branch of fermionic excitation is gapless in the naive BCS mean-field description. In this paper, we adopt a pairing-fluctuation theory to investigate the pairing fluctuation effects on the unpaired color in strongly coupled atomic color superfluids and quark color superconductors. At low temperature, a large pairing gap of the paired colors suppresses the pairing fluctuation effects for the unpaired color, and the spectral density of the unpaired color shows a single Fermi-liquid peak, which indicates the naive mean-field picture remains valid. As the temperature is increased, the spectral density of the unpaired color generally exhibits a three-peak structure: the Fermi-liquid peak remains but get suppressed, and two pseudogap-like peaks appears. At and above the superfluid transition temperature, the Fermi-liquid peak disappears completely and the all three colors exhibits pseudogap-like spectral density. The coexistence of Fermi liquid and pseudogap behavior is generic for both atomic color superfluids and quark color superconductors.