Electromagnetic backaction in a resonant Bose gas: Controlled spectral shifts and limits of local response
- 1University of Bergen
Abstract
Resonant atoms modify the electromagnetic environment that in turn determines their optical response, giving rise to a self-consistent light-matter problem at finite density. We investigate this feedback for the hydrogen Lyman- α transition using a local effective-medium description combined with an electromagnetic Green's function treatment of the atomic self-energy. Within the controlled regime, the self-consistent dressing produces a systematic density-dependent modification of the spectrum, including a shift of the spectral centroid and an asymmetric redistribution of integrated spectral weight. Comparison with a density expansion through fourth order provides an internal validity test: The local description remains quantitatively controlled up to approximately 2.0 × 10 21 m − 3 and becomes marginal above this density. Formal continuation to higher densities produces much stronger spectral restructuring, but this occurs together with the loss of perturbative and local-response control and is therefore not interpreted as a quantitative prediction of resolved high-density modes. To assess experimental relevance without assuming a microscopic hydrogen collision model, we additionally introduce a parametric collisional broadening Γ coll = n β . Collisional broadening becomes comparable to the controlled electromagnetic centroid shift for a characteristic coefficient of order 10 − 14 m 3 s − 1 . The robust prediction of the local theory is thus a density-dependent electromagnetic dressing of the resonant response, whereas its high-density breakdown identifies the regime in which a spatially resolved, nonlocal microscopic description of collective electromagnetic coupling becomes necessary.
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BibTeX
@article{fiedler2026electromagnetic,
title = {{Electromagnetic backaction in a resonant Bose gas: Controlled spectral shifts and limits of local response}},
author = {Johannes Fiedler},
journal = {Physical Review Research},
year = {2026},
month = oct,
doi = {10.1103/h6v7-fbqx},
url = {http://link.aps.org/doi/10.1103/h6v7-fbqx},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Electromagnetic backaction in a resonant Bose gas: Controlled spectral shifts and limits of local response
AU - Johannes Fiedler
PY - 2026
DA - 2026/10/29
JO - Physical Review Research
DO - 10.1103/h6v7-fbqx
UR - http://link.aps.org/doi/10.1103/h6v7-fbqx
AB - Resonant atoms modify the electromagnetic environment that in turn determines their optical response, giving rise to a self-consistent light-matter problem at finite density. We investigate this feedback for the hydrogen Lyman- α transition using a local effective-medium description combined with an electromagnetic Green's function treatment of the atomic self-energy. Within the controlled regime, the self-consistent dressing produces a systematic density-dependent modification of the spectrum, including a shift of the spectral centroid and an asymmetric redistribution of integrated spectral weight. Comparison with a density expansion through fourth order provides an internal validity test: The local description remains quantitatively controlled up to approximately 2.0 × 10 21 m − 3 and becomes marginal above this density. Formal continuation to higher densities produces much stronger spectral restructuring, but this occurs together with the loss of perturbative and local-response control and is therefore not interpreted as a quantitative prediction of resolved high-density modes. To assess experimental relevance without assuming a microscopic hydrogen collision model, we additionally introduce a parametric collisional broadening Γ coll = n β . Collisional broadening becomes comparable to the controlled electromagnetic centroid shift for a characteristic coefficient of order 10 − 14 m 3 s − 1 . The robust prediction of the local theory is thus a density-dependent electromagnetic dressing of the resonant response, whereas its high-density breakdown identifies the regime in which a spatially resolved, nonlocal microscopic description of collective electromagnetic coupling becomes necessary.
SN - 2643-1564
ER -