Two-dimensional pseudogap effects of an ultracold Fermi gas in the BCS-BEC crossover region

TL;DR

This study explores how pairing fluctuations cause pseudogap phenomena in a two-dimensional ultracold Fermi gas across the BCS-BEC crossover, revealing spatial and interaction-dependent effects on the local density of states.

Contribution

It provides a detailed analysis of pseudogap effects in 2D Fermi gases using a T-matrix approach within a trap, highlighting the spatial expansion of the pseudogap with stronger interactions.

Findings

Pseudogap appears in LDOS at the trap center in weak coupling.

The pseudogap region widens with increased pairing interaction.

Pseudogap influences the spectrum observed in photoemission experiments.

Abstract

We investigate pseudogap phenomena originating from pairing fluctuations in the BCS-BEC crossover regime of a two-dimensional Fermi gas in a harmonic trap. Including pairing fluctuations within a $T$-matrix theory and effects of a trap within the local density approximation, we calculate the local density of states (LDOS) at the superfluid phase transition temperature $T_{\rm c}$. In the weak-coupling regime, we show that the pseudogap already appears in LDOS around the trap center. The spatial region where the pseudogap can be seen in LDOS becomes wider for a strong pairing interaction. We also discuss how the pseudogap affects the spectrum of the photoemission-type experiment developed by JILA group.