Testing universality of Feynman-Tan relation in interacting Bose gases using high-order Bragg spectra

The Feynman-Tan relation, obtained by combining the Feynman energy relation with the Tan's two-body contact, can explain the excitation spectra of strongly interacting K-39 Bose-Einstein condensate (BEC). Since the shift of excitation resonance in the Feynman-Tan relation is inversely proportional to atomic mass, the test of whether this relation is universal for other atomic systems is significant for describing the effect of interaction in strongly correlated Bose gases. Here we measure the high-momentum excitation spectra of Cs-133 BEC with widely tunable interactions by using the second- and third-order Bragg spectra. We observe the backbending of frequency shift of excitation resonance with increasing interaction, and even the shift changes its sign under the strong interactions in the high-order Bragg spectra. Our finding shows good agreement with the prediction based on the Feynman-Tan relation. Our results provide significant insights for understanding the profound properties of strongly interacting Bose gases.

Automated summary

The Feynman-Tan relation, obtained by combining the Feynman energy relation with the Tan's two-body contact, explains the excitation spectra of strongly interacting K-39 Bose-Einstein condensate (BEC). By measuring the high-momentum excitation spectra of Cs-133 BEC, we observe the backbending of frequency shift of excitation resonance with increasing interaction, even changing its sign under strong interactions in the high-order Bragg spectra. This finding agrees with the prediction based on the Feynman-Tan relation and provides significant insights into the properties of strongly interacting Bose gases.