Role of temperature effects in the phenomenon of ultraslow electromagnetic pulses in Bose-Einstein condensates of alkali-metal atoms

TL;DR

This paper investigates how temperature influences the optical response and electromagnetic pulse slowing in Bose-Einstein condensates of alkali-metal atoms, using a microscopic Green-functions approach.

Contribution

It provides a detailed theoretical analysis of temperature effects on optical properties and pulse propagation in BECs, highlighting conditions where temperature impacts are negligible or significant.

Findings

Group velocity and absorption rate are nearly independent of temperature from zero to critical.

Temperature effects can become significant in specific configurations of the system.

The Green-functions formalism effectively describes the temperature-dependent optical response.

Abstract

We study the temperature dependence of optical properties of dilute gases of alkali-metal atoms in the state with Bose-Einstein condensates. The description is constructed in the framework of the microscopic approach that is based on the Green-functions formalism. We find the expressions for the scalar Green functions describing a linear response of a condensed gas to a weak external electromagnetic field (laser). It is shown that these functions depend on the temperature, other physical properties of a system, and on the frequency detuning of a laser. We compare the relative contributions of the condensate and non-condensate particles in the system response. The influence of the temperature effects is studied by the example of two- and three-level systems. We show that in these cases, which are most commonly realized in the present experiments, the group velocity and the absorption rate of pulses practically do not depend on the gas temperature in the region from the absolute zero to the critical temperature. We discuss also the cases when the temperature effects can play a significant role in the phenomenon of slowing of electromagnetic pulses in a gas of alkali-metal atoms with Bose-Einstein condensates.