# Hidden multiparticle excitation in weakly interacting Bose-Einstein Condensate

## TL;DR

This paper explores how multiparticle excitations in a weakly interacting Bose-Einstein condensate influence collective and single-particle excitations, revealing that multiparticle effects can manifest as bimodality in the density response, especially at finite temperatures.

## Contribution

It demonstrates that multiparticle excitations, typically weak at low temperatures, can become observable as bimodal features in the density response function of a BEC.

## Key findings

- Multiparticle excitations can appear as bimodality in density response.
- Spectral distinctions between single-particle and density excitations are clarified.
- Multiparticle effects emerge more prominently at nonzero temperatures.

## Abstract

We investigate multiparticle excitation effect on a collective density excitation as well as a single-particle excitation in a weakly interacting Bose--Einstein condensate (BEC). We find that although the weakly interacting BEC offers weak multiparticle excitation spectrum at low temperatures, this multiparticle excitation effect may not remain hidden, but emerges as bimodality in the density response function through the single-particle excitation. Identification of spectra in the BEC between the single-particle excitation and the density excitation is also assessed at nonzero temperatures, which has been known to be unique nature in the BEC at absolute zero temperature.