Measuring the dynamic structure factor of a quantum gas undergoing a structural phase transition
Abstract
The dynamic structure factor is a central quantity describing the physics of quantum many-body systems, capturing structure and collective excitations of a material. In condensed matter, it can be measured via inelastic neutron scattering, which is an energy-resolving probe for the density fluctuations. In ultracold atoms, a similar approach could so far not be applied due to the diluteness of the system. Here, we report on a direct, real-time and non-destructive measurement of the dynamic structure factor of a quantum gas exhibiting cavity-mediated long-range interactions. The technique relies on inelastic scattering of photons, stimulated by the enhanced vacuum field inside a high finesse optical cavity. We extract the density fluctuations, their energy and lifetime while the system undergoes a structural phase transition. We observe an occupation of the relevant quasi-particle mode on the level of a few excitations, and provide a theoretical description of this dissipative quantum many-body system.
Cite
@article{arxiv.1503.05565,
title = {Measuring the dynamic structure factor of a quantum gas undergoing a structural phase transition},
author = {Renate Landig and Ferdinand Brennecke and Rafael Mottl and Tobias Donner and Tilman Esslinger},
journal= {arXiv preprint arXiv:1503.05565},
year = {2015}
}
Comments
17 pages including supplementary information