Probing the Roton Excitation Spectrum of a Stable Dipolar Bose Gas
| Autor: | R. M. W. van Bijnen, Lauriane Chomaz, D. Petter, A. Patscheider, Manfred J. Mark, Francesca Ferlaino, G. Natale |
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| Rok vydání: | 2019 |
| Předmět: |
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 |
| Zdroj: | Physical Review Letters |
| ISSN: | 1079-7114 0031-9007 0368-3400 0038-5646 |
| DOI: | 10.1103/physrevlett.122.183401 |
| Popis: | 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. Comment: 11 pages, 8 figures |
| Databáze: | OpenAIRE |
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