Bogolon-mediated light absorption in atomic condensates of different dimensionality

TL;DR

This paper develops a microscopic theory describing how electromagnetic waves are absorbed by Bose-Einstein condensates of cold atoms across different dimensions, highlighting the role of bogolon excitations and internal degrees of freedom.

Contribution

It introduces a novel theoretical framework for electromagnetic absorption in condensates of composite bosons, considering internal structures and system dimensionality.

Findings

Absorption mediated by one and two-bogolon excitations varies with frequency.

Absorption efficiency depends on condensate density and system dimensionality.

Transitions involve internal degrees of freedom of non-condensed bosons.

Abstract

In the case of structureless bosons, cooled down to low temperatures, the absorption of electromagnetic waves by their Bose-Einstein condensate is usually forbidden due to the momentum and energy conservation laws: the phase velocity of the collective modes of the condensate called bogolons is sufficiently lower than the speed of light. Thus, only the light scattering processes persist. However, the situation might be different in the case of composite bosons or the bosons with an internal structure. Here, we develop a microscopic theory of electromagnetic power absorption by a Bose-Einstein condensates of cold atoms in various dimensions, utilizing the Bogoliubov model of a weakly-interacting Bose gas. Thus, we address the transitions between a collective coherent state of bosons and the discrete energy levels corresponding to excited internal degrees of freedom of non-condensed individual bosons. It is shown, that such transitions are mediated by one and two-bogolon excitations above the condensate, which demonstrate different efficiency at different frequencies and strongly depend on the condensate density, which influence varies depending on the dimensionality of the system.