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Supersolid phase of a spin-orbit-coupled Bose-Einstein condensate: a perturbation approach

by Giovanni I. Martone, Sandro Stringari

Submission summary

As Contributors: Giovanni Italo Martone
Arxiv Link: https://arxiv.org/abs/2107.06425v1 (pdf)
Date submitted: 2021-07-19 13:51
Submitted by: Martone, Giovanni Italo
Submitted to: SciPost Physics
Academic field: Physics
Specialties:
  • Atomic, Molecular and Optical Physics - Theory
Approach: Theoretical

Abstract

The phase diagram of a Bose-Einstein condensate with Raman-induced spin-orbit coupling includes a stripe phase with supersolid features. In this work we develop a perturbation approach to study the ground state and the Bogoliubov modes of this phase, holding for small values of the Raman coupling. We obtain analytical predictions for the most relevant observables (including the periodicity of stripes, sound velocities, compressibility, and magnetic susceptibility) which are in excellent agreement with the exact (non perturbative) numerical results, obtained for significantly large values of the coupling. We further unveil the nature of the two gapless Bogoliubov modes in the long-wavelength limit. We find that the spin branch of the spectrum, corresponding in this limit to the dynamics of the relative phase between the two spin components, describes a translation of the fringes of the equilibrium density profile, thereby providing the crystal Goldstone mode typical of a supersolid configuration. Finally, using sum-rule arguments, we show that the superfluid density can be experimentally accessed by measuring the ratio of the sound velocities parallel and perpendicular to the direction of the spin-orbit coupling.

Current status:
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Submission 2107.06425v1 on 19 July 2021

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