Colloquia

Colloquium
Friday, October 2, 2020
3:30 PM
online, Room via Zoom
Note special room.

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"Isolated Superfluid Liquid Helium Drops in a Magneto-Gravitational Trap"


Dr. Charles Brown II , University of California, Berkeley
[Host: Bellave Shivaram]
ABSTRACT:

The unique properties of superfluid 4He (low mechanical stiffness, zero viscosity, high structural and chemical purity and extremely low optical loss) may allow the direct pursuit of optomechanics with quantum mechanical oscillators. We have constructed an optomechanical system consisting entirely of a magnetically levitated drop of superfluid 4He in vacuum. Levitation removes a source of loss associated with physically clamped oscillators. and allows the drop to efficiently cool itself via evaporation. The drop’s optical whispering gallery modes (WGMs) and its surface vibrations couple to each other via the usual optomechanical interactions. We demonstrate the stable magnetic levitation of superfluid 4He drops in vacuum, and present measurements of the drops' evaporation rates, temperatures, optical modes and surface vibrations. We found optical modes with finesse ≈40 (limited by the drop's size). We found surface vibrations with decay rates 1 Hz (in rough agreement with theory). Lastly, we found that the drops reach a temperature T≈330 mK, and that a single drop can be trapped indefinitely.

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