Sound, Superfluidity, and Layer Compressibility in a Ring Dipolar Supersolid

Area of Science:

• Quantum physics
• Condensed matter physics
• Ultracold atomic gases

Background:

• Supersolids exhibit both superfluid and crystalline properties.
• Dipolar Bose-Einstein condensates allow for the creation of supersolid phases.
• Goldstone modes are gapless excitations in systems with broken continuous symmetries.

Purpose of the Study:

• To propose a protocol for exciting Goldstone modes in a supersolid dipolar Bose-Einstein condensate.
• To analyze the resulting dynamics and determine key physical parameters.
• To investigate the interplay between superfluidity and crystalline order.

Main Methods:

• Numerical solution of the extended Gross-Pitaevskii equation.
• Abrupt removal of a periodic azimuthal modulation to induce oscillations.
• Application of hydrodynamic theory for supersolids at zero temperature.

Main Results:

• The study successfully proposes a protocol to excite Goldstone modes.
• Analysis yields the two longitudinal sound velocities in the supersolid phase.
• Determination of the layer compressibility modulus and superfluid fraction (fS).

Conclusions:

• The proposed protocol effectively excites Goldstone modes in the studied system.
• The results are consistent with the hydrodynamic theory of supersolids.
• The findings align with Leggett's estimate for the nonclassical moment of inertia.