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Probing the Roton Excitation Spectrum of a Stable Dipolar Bose Gas
- Source :
- Physical Review Letters
- Publication Year :
- 2019
- Publisher :
- American Physical Society (APS), 2019.
-
Abstract
- We measure the excitation spectrum of a stable dipolar Bose--Einstein condensate over a wide momentum-range via Bragg spectroscopy. We precisely control the relative strength, $\epsilon_{\rm dd}$, of the dipolar to the contact interactions and observe that the spectrum increasingly deviates from the linear phononic behavior for increasing $\epsilon_{\rm dd}$. Reaching the dipolar dominated regime $\epsilon_{\rm dd}>1$, we observe the emergence of a roton minimum in the spectrum and its softening towards instability. We characterize how the excitation energy and the strength of the density-density correlations at the roton momentum vary with $\epsilon_{\rm dd}$. Our findings are in excellent agreement with numerical calculations based on mean-field Bogoliubov theory. When including beyond-mean-field corrections, in the form of a Lee-Huang-Yang potential, we observe a quantitative deviation from the experiment, questioning the validity of such a description in the roton regime.<br />Comment: 11 pages, 8 figures
- Subjects :
- Condensed Matter::Quantum Gases
Physics
Bose gas
Condensed matter physics
FOS: Physical sciences
General Physics and Astronomy
Roton
01 natural sciences
Instability
Momentum
Dipole
Quantum Gases (cond-mat.quant-gas)
0103 physical sciences
Condensed Matter - Quantum Gases
010306 general physics
Spectroscopy
Energy (signal processing)
Excitation
Subjects
Details
- ISSN :
- 10797114, 00319007, 03683400, and 00385646
- Volume :
- 122
- Database :
- OpenAIRE
- Journal :
- Physical Review Letters
- Accession number :
- edsair.doi.dedup.....3865a4cc504c32a090e0dc124315d238