Dark Continuum in the Spectral Function of the Resonant Fermi Polaron

TL;DR

This paper provides numerical evidence for a 'dark continuum' in the spectral function of the resonant Fermi polaron, revealing a low spectral weight region between the polaron peak and the continuum in three dimensions.

Contribution

It demonstrates the existence of a dark continuum in the spectral function of the Fermi polaron at unitarity, a novel feature not previously characterized.

Findings

Dark continuum appears at scattering lengths around 1/k_F.

The spectral weight is anomalously low in the dark continuum region.

The phenomenon occurs without a small interaction parameter.

Abstract

We present controlled numerical results for the ground state spectral function of the resonant Fermi polaron in three dimensions. We establish the existence of a "dark continuum"---a region of anomalously low spectral weight between the narrow polaron peak and the rest of the spectral continuum. The dark continuum develops when the s-wave scattering length is of the order of the inverse Fermi wavevector, $a\lesssim 1/k_{\rm F}$, i.e. in the absence of a small interaction-related parameter when the spectral weight is not expected to feature a near-perfect gap structure after the polaron peak.