Pairing and radio-frequency spectroscopy in two-dimensional Fermi gases

TL;DR

This paper theoretically explores the normal phase of strongly interacting two-dimensional Fermi gases, revealing a crossover from polarons to pseudogap regimes and explaining recent rf spectroscopy experimental results.

Contribution

It introduces a theoretical framework for understanding the polaron to pseudogap crossover in 2D Fermi gases and connects it to experimental rf spectroscopy observations.

Findings

Identification of polaron behavior in weak attraction regime

Observation of crossover to pseudogap regime with increasing attraction

Qualitative explanation of recent rf spectroscopy measurements

Abstract

We theoretically study the normal phase properties of strongly interacting two-component Fermi gases in two spatial dimensions. In the limit of weak attraction, we find that the gas can be described in terms of effective polarons. As the attraction between fermions increases, we find a crossover from a gas of non-interacting polarons to a pseudogap regime. We investigate how this crossover is manifested in the radio-frequency (rf) spectroscopy. Our findings qualitatively explain the differences in the recent rf spectroscopy measurements of two-dimensional Fermi gases [Sommer et al., Phys. Rev. Lett. 108, 045302 (2012) and Zhang et al., Phys. Rev. Lett. 108, 235302 (2012)].