Quasiparticle Energy in a Strongly Interacting Homogeneous Bose-Einstein Condensate
Physical Review Letters
American Physical Society
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Lopes, R., Eigen, C., Barker, A., Viebahn, K., Robert-de-Saint-Vincent, M., Navon, N., Hadzibabic, Z., & et al. (2017). Quasiparticle Energy in a Strongly Interacting Homogeneous Bose-Einstein Condensate. Physical Review Letters, 118 (210401)https://doi.org/10.1103/PhysRevLett.118.210401
Using two-photon Bragg spectroscopy, we study the energy of particle-like excitations in a strongly interacting homogeneous Bose-Einstein condensate, and observe dramatic deviations from Bogoliubov theory. In particular, at large scattering length $a$ the shift of the excitation resonance from the free-particle energy changes sign from positive to negative. For an excitation with wavenumber $q$, this sign change occurs at $a \approx 4/(\pi q)$, in agreement with the Feynman energy relation and the static structure factor expressed in terms of the two-body contact. For $a \gtrsim 3/q$ we also see a breakdown of this theory, and better agreement with calculations based on the Wilson operator product expansion. Neither theory explains our observations across all interaction regimes, inviting further theoretical efforts.
Is supplemented by: https://doi.org/10.17863/CAM.9210
This work was supported by the Royal Society, EPSRC (Grant No. EP/N011759/1), ERC (QBox), AFOSR, and ARO. R. L. acknowledges support from the E.U. Marie-Curie program (Grant No. MSCA-IF-2015 704832) and Churchill College, Cambridge. N. N. acknowledges support from Trinity College, Cambridge.
European Commission Horizon 2020 (H2020) Marie Sk?odowska-Curie actions (704832)
Royal Society (uf110236)
Royal Society (RG120365)
ECH2020 EUROPEAN RESEARCH COUNCIL (ERC) (682285)
External DOI: https://doi.org/10.1103/PhysRevLett.118.210401
This record's URL: https://www.repository.cam.ac.uk/handle/1810/264677