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Q: Fachverband Quantenoptik und Photonik

Q 39: Ultracold atoms, ions and BEC IV (with A)

Q 39.2: Vortrag

Donnerstag, 20. März 2014, 10:45–11:00, BEBEL E34

Measuring the resistive flow above the critical current in an atomic superfluid — •Fred Jendrzejewski, Stephen Eckel, Christopher J. Lobb, William D. Phillips, and Gretchen K. Campbell — Joint Quantum Institute, NIST and the University of Maryland

A superfluid current between two reservoirs, i.e. a source and drain, is persistent even without an external chemical potential difference between the reservoirs. However, above a critical current the superfluid flow becomes unstable and excitations are created, leading to resistive flow. To sustain such a dissipative current, an external chemical potential difference between the source and the drain must be applied.

In this presentation we report on the direct observation of both superfluid and resistive flow through a weak link in a weakly interacting atomic BEC. In our superfluid system, two weak links are used to divide a ring-shaped trap into two regions. Moving the weak links at a constant rate, allows for the creation of controlled flow between the source and the drain. Above a critical value of the weak link velocity, we observe a chemical potential difference between the distinct reservoirs which increases as a function of time. The observed time evolution can be well described in terms of a phenomenological theory incorporating explicitly the creation of excitations in form of phase slips. Such transport measurements will allow for a study of the microscopic origin of the dissipation and paves the way for more complex atomtronic devices like atomic DC squids.