Single-particle and collective excitations in a charged Bose gas at finite temperature

TL;DR

This paper investigates how single-particle and collective excitations behave in a charged Bose gas at finite temperature using dielectric formalism and RPA, revealing distinct spectral features and their relation to superfluidity.

Contribution

It provides a detailed analysis of excitation spectra in a charged Bose gas at finite temperature, highlighting differences between single-particle and collective modes within the dielectric formalism.

Findings

Single-particle spectrum forms a continuum with a double-peak structure at higher T.

Density fluctuation spectrum shows a single broadening peak.

Discussion of momentum distribution and superfluidity in the gas.

Abstract

The main focus of this work is on the predictions made by the dielectric formalism in regard to the relationship between single-particle and collective excitation spectra in a gas of point-like charged bosons at finite temperature $T$ below the critical region of Bose-Einstein condensation. Illustrative numerical results at weak coupling ($r_s = 1$) are presented within the Random Phase Approximation. We show that within this approach the single-particle spectrum forms a continuum extending from the transverse to the longitudinal plasma mode frequency and leading to a double-peak structure as $T$ increases, whereas the density fluctuation spectrum consists of a single broadening peak. We also discuss the momentum distribution and the superfluidity of the gas.