Excitation spectrum of a trapped dipolar supersolid and its experimental evidence

by G. Natale, R. M. W. van Bijnen, A. Patscheider, D. Petter, M. J. Mark, L. Chomaz, F. Ferlaino

Abstract:

We study the spectrum of elementary excitations of a dipolar Bose gas in a three-dimensional anisotropic trap across the superfluid-supersolid phase transition. Theoretically, we show that, when entering the supersolid phase, two distinct excitation branches appear, respectively associated with dominantly crystal and superfluid excitations. These results confirm infinite-system predictions, showing that finite-size effects play only a small qualitative role, and connect the two branches to the simultaneous occurrence of crystal and superfluid orders. Experimentally, we probe compressional excitations in an Er quantum gas across the phase diagram. While in the Bose-Einstein condensate regime the system exhibits an ordinary quadrupole oscillation, in the supersolid regime we observe a striking two-frequency response of the system, related to the two spontaneously broken symmetries.

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Reference:

Excitation spectrum of a trapped dipolar supersolid and its experimental evidence,
G. Natale, R. M. W. van Bijnen, A. Patscheider, D. Petter, M. J. Mark, L. Chomaz, F. Ferlaino,
Phys. Rev. Lett., 123, 050402, 2019.

Bibtex Entry:

@article{1907.01986,
Author = {G. Natale and R. M. W. van Bijnen and A. Patscheider and D. Petter and M. J. Mark and L. Chomaz and F. Ferlaino},
Title = {Excitation spectrum of a trapped dipolar supersolid and its experimental evidence},
  journal = {Phys. Rev. Lett.},
  volume = {123},
  issue = {5},
  pages = {050402},
  numpages = {6},
  year = {2019},
  month = {Aug},
abstract = {We study the spectrum of elementary excitations of a dipolar Bose gas in a three-dimensional anisotropic trap across the superfluid-supersolid phase transition. Theoretically, we show that, when entering the supersolid phase, two distinct excitation branches appear, respectively associated with dominantly crystal and superfluid excitations. These results confirm infinite-system predictions, showing that finite-size effects play only a small qualitative role, and connect the two branches to the simultaneous occurrence of crystal and superfluid orders. Experimentally, we probe compressional excitations in an Er quantum gas across the phase diagram. While in the Bose-Einstein condensate regime the system exhibits an ordinary quadrupole oscillation, in the supersolid regime we observe a striking two-frequency response of the system, related to the two spontaneously broken symmetries.},
  publisher = {American Physical Society},
  doi = {10.1103/PhysRevLett.123.050402},
  url = {https://link.aps.org/doi/10.1103/PhysRevLett.123.050402},
arXiv = {https://arxiv.org/abs/1907.01986}
}