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Critical superfluid velocity in a trapped dipolar gas
Ryan M Wilson1, Shai Ronen, John L Bohn
1JILA and Department of Physics, University of Colorado, Boulder, Colorado 80309-0440, USA. rmw@colorado.edu
Physical Review Letters
|April 7, 2010
Summary
We explored superfluidity in dipolar Bose-Einstein condensates (BECs). The roton in the quasiparticle spectrum lowers the critical velocity, enabling simultaneous measurement of Landau critical velocity and roton presence in experiments.
Area of Science:
- Quantum physics
- Atomic, molecular, and optical physics
Background:
- Bose-Einstein condensates (BECs) exhibit superfluidity, a frictionless flow state.
- Dipolar BECs possess unique properties due to long-range anisotropic interactions.
- The Landau criterion defines the critical velocity for superfluidity based on elementary excitations.
Purpose of the Study:
- To investigate the superfluid critical velocity of a dipolar Bose-Einstein condensate (BEC) in a 3D trap.
- To analyze the influence of the roton excitation on superfluid properties.
- To propose an experimental method for measuring Landau critical velocity and detecting rotons in dipolar BECs.
Main Methods:
- Applied the Landau criterion to the discrete quasiparticle spectrum of the dipolar BEC.
- Performed direct numerical simulations of condensate depletion using a moving blue-detuned laser.
- Varied the particle number to tune the dispersion relation and the roton minimum.
Main Results:
- The presence of the roton excitation was found to reduce the superfluid critical velocity.
- This reduction occurs beyond a critical particle number, dependent on the roton minimum.
- Numerical simulations confirmed the theoretical predictions regarding condensate depletion and critical velocity.
Conclusions:
- The roton excitation significantly impacts the superfluid critical velocity in dipolar BECs.
- The tunability of the roton minimum offers a method to probe superfluidity.
- A proposed experiment can simultaneously measure Landau critical velocity and demonstrate roton presence in dipolar BECs.
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