Towards a QMC-based density functional including finite-range effects: excitation modes of a $^{39}$K quantum droplet

TL;DR

This paper investigates how finite-range effects influence the excitation spectra of dilute $^{39}$K quantum droplets, using a density functional derived from quantum Monte Carlo calculations, revealing measurable differences from extended Gross-Pitaevskii theory.

Contribution

The study introduces a density functional based on first-principles quantum Monte Carlo calculations to incorporate finite-range effects into the analysis of quantum droplet excitations.

Findings

Finite-range effects cause up to 20% differences in excitation spectra.

The approach provides a new way to observe finite-range effects experimentally.

Results improve understanding of quantum droplet dynamics.

Abstract

Some discrepancies between experimental results on quantum droplets made of a mixture of $^{39}$K atoms in different hyperfine states and their analysis within extended Gross-Pitaevskii theory (which incorporates beyond mean-field corrections) have been recently solved by introducing finite-range effects into the theory. Here, we study the influence of these effects on the monopole and quadrupole excitation spectrum of extremely dilute quantum droplets using a density functional built from first-principles quantum Monte Carlo calculations, which can be easily introduced in the existing Gross-Pitaevskii numerical solvers. Our results show differences of up to $20\%$ with those obtained within the extended Gross-Pitaevskii theory, likely providing another way to observe finite-range effects in mixed quantum droplets by measuring their lowest excitation frequencies.