Josephson Junction Arrays with Bose-Einstein Condensates

TLDR

The study introduces a superfluid Bose‑Einstein condensate array that enables exploration of phenomena inaccessible to superconducting Josephson junctions and connects condensate dynamics with discrete nonlinear media physics. The array is formed by a laser standing wave that traps condensates in potential valleys and weakly couples them across interwell barriers, while coherence of tunneling between wells is monitored via atomic interference. The experiment directly observes oscillating atomic currents in the condensate array, showing that the square of the small‑amplitude oscillation frequency scales with the tunneling rate and yields a direct measurement of the Josephson critical current versus barrier height.

Abstract

We report on the direct observation of an oscillating atomic current in a one-dimensional array of Josephson junctions realized with an atomic Bose-Einstein condensate. The array is created by a laser standing wave, with the condensates trapped in the valleys of the periodic potential and weakly coupled by the interwell barriers. The coherence of multiple tunneling between adjacent wells is continuously probed by atomic interference. The square of the small-amplitude oscillation frequency is proportional to the microscopic tunneling rate of each condensate through the barriers and provides a direct measurement of the Josephson critical current as a function of the intermediate barrier heights. Our superfluid array may allow investigation of phenomena so far inaccessible to superconducting Josephson junctions and lays a bridge between the condensate dynamics and the physics of discrete nonlinear media.