|M.Sc Student||Itay Shomroni|
|Subject||Observation of the d.c. Josephson Effect in a Bose-Einstein|
Condensate of Dilute Atomic Vapor
|Department||Department of Physics||Supervisor||Professor Steinhauer Jeff|
|Full Thesis text|
We observe the d.c. Josephson effect in a junction of two clouds of quantum-coherent, Bose-Einstein condensed atomic vapor. This is the first observation of this effect in a system other than a superconducting junction.
The d.c. Josephson effect was initially predicted for superconducting systems and extensively studied in those systems. In the d.c. Josephson effect, particle current flows between two weakly coupled quantum fluids with no accompanying potential difference. The current depends explicitly on the quantum phase difference between the fluids. The direct relation between observable (current) and quantum (phase) quantities make the d.c. Josephson effect a unique tool for studying quantum phenomena.
Bose-Einstein condensed dilute atomic vapors (BECs) are a recent addition to the family of systems exhibiting quantum coherence, for which the d.c. Josephson effect is applicable. In the experimental system, an atomic Josephson junction is realized. Two BECs in a magnetic trap are separated with a narrow potential barrier created using a laser beam. Atomic tunneling current can be applied between the two BECs by sweeping the laser beam across the magnetic trap, and the ensuing (chemical) potential difference can be measured. An analysis of the current-potential difference relation reveals a regime where the d.c. Josephson effect is apparent, in which no potential difference accompanies current flow through the junction.
This is the first experimental generalization of the d.c. Josephson effect, showing that systems of vastly different qualitative nature, namely electron pairs in superconductors and neutral atoms in BECs, behave in a qualitative similar manner.