How do sound waves in a Bose-Einstein condensate move so fast?

How do sound waves in a Bose-Einstein condensate move so fast?

Low-momentum excitations of a dilute Bose-Einstein condensate behave as phonons and move at a finite velocity vs. Yet the atoms making up the phonon excitation each move very slowly; va = p/m → 0. A simple “cartoon picture” is suggested to understand this phenomenon intuitively. It implies a relation vs/va ≈ Nex, where Nex is the number of excited atoms making up the phonon. This relation does ...

Fast rotation of a Bose-Einstein condensate.

We study the rotation of a 87Rb Bose-Einstein condensate confined in a quadratic plus quartic potential. This trap configuration allows one to increase the rotation frequency of the gas above the trap frequency. In such a fast rotation regime we observe a dramatic change in the appearance of the quantum gas. The vortices which were easily detectable for a slower rotation become much less visibl...

Propagation of sound in a Bose-Einstein condensate

Sound propagation has been studied in a magnetically trapped dilute Bose-Einstein condensate. Localized excitations were induced by suddenly modifying the trapping potential using the optical dipole force of a focused laser beam. The resulting propagation of sound was observed using a novel technique, rapid sequencing of nondestructive phase-contrast images. The speed of sound was determined as...

Observation of shock waves in a large Bose-Einstein condensate

We observe the formation of shock waves in a Bose-Einstein condensate containing a large number of sodium atoms. The shock wave is initiated with a repulsive blue-detuned light barrier, intersecting the BoseEinstein condensate, after which two shock fronts appear. We observe breaking of these waves when the size of these waves approaches the healing length of the condensate. At this time, the w...

Vortex patterns in a fast rotating Bose-Einstein condensate