Spectral weight suppression in response functions of ultracold fermion-boson mixtures

TL;DR

This paper investigates how spectral weight suppression occurs in the response functions of ultracold fermion-boson mixtures, revealing effects on Bragg spectra and force correlations, especially at low impurity densities.

Contribution

It introduces a diagrammatic approach with vertex corrections to accurately reproduce spectral weight suppression effects previously observed in simulations.

Findings

Spectral weight suppression occurs at small momentum where impurity and phonon modes intersect.

Bragg spectra and force-force correlations are heavily influenced by spectral weight suppression.

Vertex corrections are essential for accurately modeling the suppression effects.

Abstract

We study the dynamical response of ultracold fermion-boson mixture in the Bogoliubov regime, where the interactions between fermionic impurities and bosonic excitations (phonons) are described by an effective Frohlich model under the Bogoliubov approximation. A characteristic suppression of the single-particle spectral weight is found in the small momentum region where the impurity band and phonon mode intersect. Using diagrammatic technique we compute the Bragg spectra as well as the momentum dependent force-force correlation function. We fnd that both of them are heavily affected by the spectral weight suppression effect at low impurity densities in both 1D and 2D systems. We show that the the spectral weight suppression feature in Bragg spectra, which was previously found in the quantum Monte Carlo simulations and which cannot be recovered by the random phase approximation, can be accurately reproduced with the help of vertex corrections.